02 July 2010

Trust

Posts relating to the category tag "trust" are listed below.

02 July 2010

Web Site Security Basics for SMEs

Sometimes when I'm out socially and people ask what I do, the conversation progresses to concerns about their own web site. They may have a hobby site, run a micro-business or be a manager or director of a small and medium-sized enterprise (SME)—there's all sorts of great entrepreneurial activity going on.

It is very common for SMEs not to have much time or budget for information security, and the available information can be poor or inappropriate (ISSA-UK, under the guidance of their Director of Research David Lacey, is trying to improve this). But what can SMEs do about their web presence—and it is very unusual not to have a web site, whatever the size of business.

Photograph of a waste skip at the side of St John Street in Clerkenwell, London, UK, with the company's website address written boldly across it

Last week I was asked "Is using <company> okay for taking online payments?" and then "what else should I be doing?". Remember we are discussing protection of the SME's own web site, not protecting its employees from using other sites. If I had no information about the business or any existing web security issues, this is what I recommend checking and doing before anything else:

  • Obtain regular backup copies of all data that changes (e.g. databases, logs, uploaded files) and store these securely somewhere other than the host servers. This may typically be daily, but the frequency should be selected based on how often data changes and how much data the SME might be prepared to lose in the event of total server failure.
    • check backup data can read and restored periodically
    • don't forget to securely delete data from old backups when they are no longer required
  • Use a network firewall in front of the web site to limit public (unauthenticated user) access to those ports necessary to access the web site. If other services are required remotely, use the firewall to limit from where (e.g. IP addresses) these can be used.
    • keep a record of the firewall configuration up-to-date
    • limit who can make changes to the firewall
  • Ensure the host servers are fully patched (e.g. operating system, services, applications and supporting code), check all providers for software updates regularly and allow time for installing these.
    • remove or disable all unnecessary services and other software
    • delete old, unused and backup files from the host servers
  • Identify all accounts (log in credentials) that provide server access (not just normal web page access), such as used for transferring files, accessing administrative interfaces (e.g. CMS admin, database and server management/configuration control panels) and using remote desktop. Change the passwords. Keep a record of who has access and remove accounts that are no longer required and enable logging for all access using these accounts.
    • restrict what each account can do as much as possible
    • add restrictions to the use of these accounts (e.g. limit access by IP address, require written approval for use, keep account disabled by default)
  • Check that every agreement with third parties that are required to operate the web site are in the organisation's own name. These may include the registration of domain names, SSL certificates, hosting contracts, monitoring services, data feeds, affiliate marketing agreements and service providers such as for address look-up, credit checks and making online payments.
    • ensure the third parties have the organisation's official contact details, and not those of an employee or of the site's developers
    • make note of any renewal dates
  • Obtain a copy of everything required for the web site including scripts, static files, configuration settings, source code, account details and encryption keys. Keep this updated with changes as they are made.
    • verify who legally owns the source code, designs, database, photographs, etc.
    • check what other licences affect the web site (e.g. use of open source and proprietary software libraries, database use limitations).

Do what you can, when you can. Once those are done, then:

  • Verify the web site and all its components (e.g. web widgets and other third party code/content) does not include common web application vulnerabilities that can be exploited by attackers (e.g. SQL injection, cross-site scripting).
  • Check what obligations the organisation is under to protect business and other people's data such as the Data Protection Act, guidance from regulators, trade organisation rules, agreements with customers and other contracts (e.g. PCI DSS via the acquiring bank).
    • impose security standards and obligations on suppliers and partner organisations
    • keep an eye open for changes to business processes that affect data
  • Document (even just some short notes) the steps to rebuild the web site somewhere else, and to transfer all the data and business processes to the new site.
    • include configuration details and information about third-party services required
    • think about what else will need to be done if the web site is unavailable (does it matter, if so what exactly is important?)
  • Provide information to the web site's users how to help protect themselves and their data.
    • point them to relevant help such as from GetSafeOnline, CardWatch and Think U Know
    • provide easy methods for them to contact the organisation if they think there is a security or privacy problem
  • Monitor web site usage behaviour (e.g. click-through rate, session duration, shopping cart abandonment rate, conversion rate), performance (e.g. uptime, response times) and reputation (e.g. malware, phishing, suspicious applications, malicious links) to gather trend data and identify unusual activity.
    • web server logs are a start, but customised logging is better
    • use reputable online tools (some of which are free) to help.

That's just the basics. So, what would be next for an SME? If the web site is a significant sales/engagement channel, the organisation has multiple web sites, is in a more regulated sector or one that is targetted particularly by criminals (e.g. gaming, betting and financial), takes payments or does other electronic commerce, allows users to add their own content or processes data for someone else, the above is just the start. Those SMEs probably need to be more proactive.

This helps to protect the SME's business information, but also helps to protect the web site users and their information. After all, the users are existing and potential customers, clients and citizens.

Oh, the best response I had to someone when I was explaining my work: "You're an anti-hacker than?". Well, I suppose so, but it's not quite how I'd describe it.

Any comments or suggestions?

Posted on: 02 July 2010 at 08:18 hrs

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30 April 2010

Software Assurance Labelling

An article about the upcoming new regime for the classification and labelling of chemicals reminded me to write about software assurance (i.e. software security) labelling (and since web sites are software). From 1 December 2010, the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS) comes into force, implemented in Europe by the Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures (CLP), amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006.

Four type of warning labels - a skull and crossbones indicating acute toxicity, an exclamation mark indicating other harm, an exploding bomb indicating an explosive substance and the profile of a human's head and shoulders indicating hazardous to human health

CLP implications and guidelines are explained by the UK Health and Safety Executive (HSE) but are defined fully in the UN's documentation. The headline chemical labelling indicates the potential damage/harm that can occur, rather than the content/properties of the agent. I like this "impact" approach. Nutritional labelling on the other hand generally tends to focus on ingredients and their properties, but some food labelling is also beginning to attempt to classify low/medium/high fat/saturates/sugars/salt levels, which is more akin to the impact approach.

Jeff Williams (CEO of Aspect Security and Chair of OWASP Foundation) proposed a Software Facts label five years ago at OWASP Appsec Europe. This would be similar to appliance energy usage labels, food nutrition facts label, material safety data sheets or laser safety classes. That idea was taken up by NIST and the Software Assurance Consortium (SwAC) to develop another proposal.

Comment here and here around the same time in 2005 describes some of the challenges. Indeed many more aspects of the software development lifecycle impact upon the creation of secure software. But simplicity is needed in the presentation of such information—perhaps some high-level impact related indicators augmented by the more detailed information for different audiences (e.g. users, operators, administrators, system achitects). SwAC's version seems to be somewhat aimed at software development teams, instead of people in end user organisations, especially those involved with procurement decisions. Whilst some people will want to know the data behind a classification, most businesses and consumers will need something more akin to the CLP headline labels relating to business (or personal) impact as a starting point for their decisions.

  • How dangerous is this software?
  • How reliable is it?
  • How does it affect privacy?
  • How does the IT environment affect these?
  • How are these affected by changing the default settings?

This a big challenge. Just specifying the privacy practices for a web site can be complex. ENISA's Common Assurance Maturity Model (CAMM) project is trying to define how cloud service providers can be compared to allow users to make informed decisions about the risks. Perhaps that project will develop into some form of labelling scheme, or at least provide ways for typical consumers of the services to determine their own risks as simply as possible.

I don't know the status of the SwAC project but will now make the effort to find out.

Posted on: 30 April 2010 at 08:49 hrs

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30 March 2010

Let Down By Customer Surveys

Almost every sale, citizen enquiry and support request now seems to lead to being asked to complete an online customer survey. Almost without exception, the user experience, privacy and security of these online customer surveys are worse than the service being asked to comment on. Here are a couple of customer surveys I was asked to complete last week.

Partial screen capture of an online customer survey web page showing a browser alert message asking the user 'Do you want to view only the webpage content that was delivered securely? This webpage contains content that will not be delivered using a secure HTTPS connection, which could compromise the security of the entire webpage' with buttons for More Info, Yes and No

Problems with using SSL, such as shown above, do occur but more often than not people are asked to submit personal identifiable information and other forms of personal data without the use of SSL. Bad layout, poorly designed questions, missing privacy notices and improper validation are extremely common. Many forms have mis-configured web sites that give away sensitive information about how the site and server are set up when they don't work:

Partial screen capture of an online customer survey web page showing an error message on submission of the customer feedback form stating 'There was an error processing your save please try again later.
at Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value) at Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(Object Value) at ************.completeScorecardDependency.Save(String ButtonClicked) in D:\wwwroot\**************\feedback\completeScorecardDependency.aspx.vb:line 831 Conversion from string

And on Saturday I was given a coupon given at a shop's physical checkout to provide feedback on how they did with the chance of winning an iPod or cash for doing so. Yesterday I typed in the URL from the coupon, entered the required store code, and... that was the end of that marketing exercise:

Partial screen capture of an online customer survey web page with a trapped error message stating the server had encountered an error internal error 'which prevented it from fulfilling the request. Your session may have timed out. Try re-starting your web browser and re-enter the URL on your survey invite'

I didn't time out as the message suggested, unless you have less than 5s to answer one question. Perhaps there is only one custom error page for all server-side errors, or the wrong error page is assigned? Points for hiding internal error messages, but still a failure.

Is 3/3 customer surveys tried in the last fortnight broken just bad luck? Or does it indicate a poor standard of such efforts? One of these is an international consumer brand, another a major UK High Street retailer and the other, a medium-sized business services company. I can't quite remember the the previous customer survey to these three, but I think it may have been a salary/skill survey. That had poorly thought-out questions and although it didn't obviously fail, it did ask me to log in on submission. So I'm not sure if that meant my efforts had been saved or not.

Do all these problems and errors mean the data from other people's forms that were successfully submitted (if any) are less valid? I can imagine management decisions are being made as a result of the survey feedback (if not, why waste everyone's time?). What is the effect on data quality? It could be that some forms fail when a particular answer is selected or left blank—this could be important marketing knowledge, and if no responses include the particular option it may be incorrectly assumed no-one selected it. The management decisions will be being based on poor data.

Perhaps part of the problem is that customer surveys are often managed, operated and hosted by third parties due to the ease of implementation. But "easy" doesn't mean it meets your own organisation's standards, or general good practice. You are still accountable for the web issues and it's your organisation's reputation that will be affected detrimentally.

Good design, privacy and security impact assessments, thorough testing and verification are required like any other other addition to a web site. Analytics should be used to track survey users through forms and this data combined with server logs of access and errors generated by the web server. Prove your marketing data are valid before you use it in business decisions.

Posted on: 30 March 2010 at 09:25 hrs

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26 February 2010

Identifiability and Traceability Online

Last month I described the ability to track users sessions with browser data. A recent posting on IT Law in Ireland highlighted a series of blog posts elsewhere that give further insight into what is possible.

Photograph of the exhibit 'L-E-D-LED-L-ED' by Dilight at the London Design Museum, consisting of hundreds of bead-shaped light emitting diodes (LEDs) that can slide back and forth along a series of horizontal wires

Well, I just got round to reading them properly. The posts on Freedom to Tinker by David Robinson and Harlan Yu are:

The conclusion? It is possible to trace and identify individuals easier than you may think. We are dropping evidence like dead skin cells as we traverse the internet. Fact or fiction? Well the US Defense Advanced Research Projects Agency (DARPA) are taking it seriously with a recent call for research into cyber genetics, cyber anthropology and cyber physiology in its Cyber Genome Program. DARPA hopes to develop advanced methods to fingerprint or identify the origins of a cyber attacks by examining digital artifacts, and presumably other criminal activities utilising computer technology.

Getting a bit more down to earth, web site owners need to consider what information is being gathered and why, ensure this is legal, check that consent is implied or has been explicitly given for the purposes and what monitoring and analysis is performed on the data. It could be easy for system developers to carried away with tracking and tagging. Contracts with third parties should state clearly what the expectations are about the security and privacy of information, to protect web site users (employees, customers, clients, citizens) and the business.

Posted on: 26 February 2010 at 09:06 hrs

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23 February 2010

Store Locator - Software Bug or Security Vulnerability?

Testing a web site is important, and smoke/regression testing would normally be undertaken each time the web site's code is updated or extended. But what about third party code and data on your web site? I was using a shop's store locator and it wrongly identified the two closest store locations to Farringdon Station in Clerkenwell, EC1M. Both Euston Station NW1 and Canary Wharf E14 are further away than the third result, Cheapside.

Partial screen capture showing the website's store locator search for 'Farringdon, London, EC1M, UK' revealing the nearest stores as Euston Station NW1 and Canary Wharf E14, followed by Cheapside EC4M and Covent Garden WC2E, with full address details masked

Intrigued, I zoomed in on the map and the ordering of the first two results swapped. And the data point for Canary Wharf seems to be located in the centre of the City of London, instead of its actual location downriver on the Isle of Dogs. The data point for the first result wasn't even displayed.

Partial screen capture showing the generated Virtual Earth map positioning Canary Wharf 5 miles off-position in the middle of the City of London

So is this a third party problem, or something else? Well, without investigating further you can't really tell, but it's the concept that matters.

This inaccuracy is worrying for a number of reasons:

  • Customers may have difficulty locating shops.
  • It undermines customer confidence and therefore trust in the brand.
  • It indicates a lack of care in the web site's development and may put off online shoppers.
  • It could indicate the presence of a security vulnerability which could be exploited to damage the site, its data or its users.
  • The same geo-location code may be used for other internal calculations such as marketing data processing that affect business decisions.

If you are including functionality or data from third parties, you need to know when that system or service is updated. This notification requirement should be built into contracts. In this case, the data being returned may be inaccurate, formatted in an unxpected manner or be exposing a fault in your own processing of the data. Undertaking input validation on the data provided by the third party and output validation on what you are about to send back to the web site user need to test for reasonableness as well as more technical checks. Why not cross-check that the first result's postcode is closer than the second and the third?

It may just be a problem with the company's own data, but that's even more worrying.

Posted on: 23 February 2010 at 11:12 hrs

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01 January 2010

NAI Code Compliance Report 2009

Following on from Tuesday's topic of terms and conditions for interactive advertising, the US Network Advertising Initiative (NAI) has just released their 2009 compliance report.

Members that collect, transfer, or store data for use in OBA [Online Behavioral Advertising], Multi-Site Advertising and/or Ad Delivery & Reporting shall provide reasonable security for that data.

The NAI is an association of 35 US advertising networks, data exchanges, and marketing analytics services providers including Advertising.com, Google and Yahoo.

The NAI Compliance Report 2009 discusses compliance by its members with its self-regulatory code of conduct governing the collection, use, and disclosure of data for online advertising services by its member companies (the NAI Code). The NAI Code has its own definition of personally identifiable information (PII) and sensitive information and its own protection principles. The NAI found its members to be broadly in compliance with the code, apart from ten members that did not disclose specific retention periods for data collected.

Whatever your views of behavioural advertising, industry initiatives like this to improve, and report on, standards are a welcome contribution. No doubt the code will evolve over time, but it is a good starting point. The code perhaps lacks requirements for measuring the accuracy of data or requiring ways for consumers to correct information about themselves, and it would be useful to know what checks are being undertaken as part of the audit. For example "Reasonable security is determined in light of several factors including, but not limited to, the sensitivity of the data, the nature of a company's business operations, the types of risks a company faces, and the reasonable protections available to a company" could be interpreted in a number of ways and some guidance on what is "reasonable" both from the organisation and individual's points of view would be welcome.

P.S. Happy new year.

Posted on: 01 January 2010 at 14:57 hrs

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22 December 2009

Should The Whole Web Site Be SSL?

Britain has some snowy and cold weather at the moment causing difficulty for people getting to shops or going on holiday, and web retailers are likely to be doing brisk trade if they can still deliver before Christmas.

Photograph of the snow-covered landscape around Gatehouse, Northumberland yesterday 21 December 2009

E-commerce sites are often associated with HTTPS (a combination of HTTP with the SSL/TLS cryptographic protocol). There was a time when HTTPS was used only where absolutely necessary due to the additional encryption/decryption overhead it placed on a user's browser (client) and the web application (server). But what's the situation today?

N.B. the padlock symbol or green/blue coloured address bar (depending upon the type of certificate in use) indicating the use of a "secure" web server, does not mean your data is safe; it shows the server identity is verified to a certain extent and that data in transit between your web browser and the web server is probably safe from interception, if it is configured correctly on the server, the certificate has not expired or been revoked, and you can ensure the content you see is on the site the address bar says it is. It also says nothing about how the organisation and partners that handle the data once it has been received by the web server—they might forward it by email, allow third parties to have access to the server, print the data and leave it unprotected, etc.

Almost all web sites have some aspects that should only be accessible over HTTPS. Any sort of data entry form is likely to include personal information and therefore HTTPS should be used to at least protect the confidentiality of the information in transit. User registration, authentication (log in) and any pages that contain confidential information would also be included. Previously, many search engines did not index HTTPS addresses, but since its use was mainly restricted to content protected by some type of authentication and authorisation, this was never much of a concern.

But nowadays, search engines are indexing HTTPS content and a few web sites are only available using HTTPS. Is this a configuration worth following? In a discussion Ivan Ristić described the additional benefits of HTTPS (HTTP over SSL):

... Even with web sites that do not contain sensitive content (no need for confidentiality), you'd still want SSL to provide authentication (are you seeing the correct web site?) and integrity (has anyone modified content in transit?)... Can you have too much SSL? I don't think so.

Issues

So while there are benefits relating to authenticity and integrity, in addition to confidentiality, and dangers to mixing HTTP and HTTPS on the same site due to badly designed authorisation and session management systems, what other issues are there?

Search engines

The most popular search engine robots no longer discriminate whether the content is HTTP or HTTPS, so this is no longer a concern. I am not aware if any adverse effect on search engine optimisation (SEO), other than the effects of changing from HTTP to HTTPS or vice versa which would have to be managed carefully and appropriate permanent redirects set up (also called 301 redirect due to the HTTP response status code of 301 for "moved permanently").

Note that Google, and apparently Yahoo and Microsoft, support the "rel='canonical'" link element and state it can be used for indicating a preference for HTTP vs HTTPS, or vice versa, when pages are available by both. There is also a setting for this choice in Google webmaster tools if you are a site owner. But be careful with allowing both HTTP and HTTPS access to the same page, since this quite often is implemented in a way that adds vulnerabilities to user authentication and session management.

Resources on the server

The server is affected by two aspects—the increased number of requests (see also resources on the client, below) and the overhead of encryption/decryption/building SSL connection. Intermediate proxies should not cache the content and therefore a greater number of requests is to be expected. The additional resources required to serve content using HTTPS are discussed extensively here and in a research paper, i.e. there will be a performance hit, but whether this is a problem depends on your traffic profile, architecture, server utilisation and site's design.

Server side processes

It is possible that any server-side indexing or reporting systems may not support HTTPS and they may need to be updated or configured to work with the different protocol. If you syndicate data to other systems via XML, RSS or web services, these processes will also need to be checked for compatibility.

Traffic management

Network devices that inspect and route internet traffic must be SSL-aware to be able to read and analyse the content. Most modern devices will be able to support this mode of operation.

Client device support

Some devices (e.g. mobile) may not support HTTPS, or HTTPS may not be allowed through firewalls but this is probably less of an issue now. Check if these are issues with your expected users and the devices your site supports.

Address familiarity

Most people will not recognise (or type in) HTTPS addresses and use the common shorthand of the host name (e.g. www.clerkendweller.com) or an alias (e.g. clerkendweller.com) rather than the protocol followed by the full host name. So this would require a redirect from the HTTP address to the HTTPS one, and for many web sites this will be acceptable. For sites of a more sensitive nature, this would have to be handled carefully to protect any session identifiers and still leaves the user potentially vulnerable to a man in the middle (MITM) attack. These are where the redirect is amended and the user taken to a malicious web site instead. If you can rely on users using only the SSL address, perhaps by bookmarking it, you are on safer territory.

Resources on the client

Again there will be a performance hit on the user's client device (e.g. browser of a desktop computer). Much of the time this will not be a problem unless the device already lacks resources (e.g. a mobile device). Then again, due to the lack of caching, more requests will have to be made directly to the server, creating additional lag to download and build content.

Mixed content

Even if all the content from your own site is sent using HTTPS, you may have embedded content such as:

  • client-side web analytics
  • advertisements
  • news feeds
  • widgets
  • images, videos, scripts and other content hosted elsewhere.

These must also all be provided using HTTPS, otherwise the benefit of being HTTPS-only will be lost and users may see "mixed content" warning. But this can be a problem as much third-party content is not available using HTTPS (SSL), notably including Google AdSense, Amazon Affiliates and YouTube. However, Google Analytics does support SSL.

Conclusions and further reading

An all-HTTPS web site provides additional security benefits, but user acceptance and server constraints need to be considered in the site's design and architecture decision making processes. The partial, or full, use of HTTPS (SSL) in a web site needs to be considered carefully during design and development to ensure weaknesses that could be exploited are not built in, and then verified by thorough testing. If you have a heavily consumer-focused web site or include third-party content, some of the choices may have to be on the side of ease of use rather than with the lowest security risk.

"Whole site SSL" should be a serious consideration for "green field" web sites, especially where user authentication is required for any part of the content and for sites where phishing is a major risk (e.g. gaming, web mail, banking). User knowledge and acceptance may be difficult until we see the likes of major banks or large consumer-orientated sites (Google Mail, Google Docs, Twitter, Facebook) use this configuration and and display a warning/educational message to people who go to the non HTTPS site, rather than a redirect.

Posted on: 22 December 2009 at 09:12 hrs

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16 October 2009

Warning: Punctuation Marks Can Damage Your Web Site

It seems a missing full stop brought down every web site hosted on a domain ending with .se (the top-level domain for Sweden) on Monday evening.

Partial picture of Table 4/T.50, the basic 7-bit code table, from the ITU-T Recommendation T.50

The .SE registry had apparently performed an incorrect software update but actually a script (program written by a human) had failed to add a terminating full stop (.) to the DNS records in the .se zone. Tested? I guess not.

It reminded me of Google's mishap in May when it flagged every site as potentially harmful by simply adding an extra forward slash (/) character to a file.

And, simple punctuation mistakes can invalidate the HTML of your web page, or stop your application's scripts from running. In July Microsoft created a security flaw in Windows by the addition of an extra ampersand (&) character.

Tim Berners-Lee is still wishing he hadn't put two forward slashes in every URL.

The mighty power of a punctuation mark.

Posted on: 16 October 2009 at 15:24 hrs

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02 October 2009

Don't Mix and Match Those Domains

Many organisations like to do land grab with domain names by purchasing the same name with different generic top-level domains (e.g. .com, .net, .info), country code top-level domains (e.g. .uk, .es, .fr), and multiple second-level domains (e.g. .co.uk, .org.uk). Then of course there are mis-spellings, similar sounding words, brand names and trademarks.

Well all that leads to complexity, and it's not uncommon for many domains to be aliased to the same site in a way that any of them can be used to access the complete web site.

But it can get especially messy when SSL is enabled on some or all of the site too. Inevitably there end up being certificate warnings. Some organisations should know better. So when I was searching for providers of online and business privacy "seals",

Partial screen capture showing search engine results including SSL links to pages on the www.truste.org domain including https://www.truste.org/pvr.php?page=complaint

I was very surprised to click on the link to an SSL page which was reported as using an invalid certificate.

Partial screen capture showing the browser's warning message about the page's SSL certificate that says 'www.truste.org uses an invalid security certificate' and 'The certificate is only valid for *.truste.com'

Actually the certificate was fine, it just wasn't valid for the .ORG domain. Perhaps they had hoped the wildcard SSL certificate *.trust.com would somehow cater for *.truste.* - no.

Partial screen capture showing the browser's information about the certificate which says 'You are about to override how Firefox identifies this site - Legitimate banks, stores and other public sites will not ask you to do this' and 'Certificate belongs to a different site, which could indicate an identity theft'

Identity theft? Privacy? But apart from these configuration issues, isn't it just very confusing to have many different domains appearing in search engine results? How does this duplicate content affect their search engine ranking? Does it undermine trust in the brand? Should the SSL part of the site be indexed at all? Perhaps. Who makes these decisions? Is it the developers, the person who configured the site or does the business have a viewpoint?

I overheard a (loud) mobile telephone conversation this week in which a marketing manager* was apologising for a problem but they "did not know any of the technicalities". Mmmm, who is accountable? Make it your business to know.

[* Security and technology managers should also understand their organisation's business objectives.]

Posted on: 02 October 2009 at 07:56 hrs

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29 September 2009

IP Address Restrictions and Exceptions

It's common for access to some web sites to be restricted to users from particular Internet Protocol (IP) addresses. This is usually in addition to some other identification and authentication method. But other IP addresses are often added to this "allow list" and these should not necessarily be trusted in the same way.

Photograph of a sign with an exclamation mark on a yellow triangle that reads 'Caution - Traffic management Trial - DO NOT MOVE' on a construction site boundary's wire barrier

In a typical scenario, a web site hosted on the internet that is used to administer another web application might be restricted to the company's own IP addresses. Then the developers say they need to check something on the live site, or another server needs to index the content, or someone wants to work from home for a while, or the site needs to be demonstrated at a client's location. All these additional IP addresses are added to the "allow list". These restrictions may be being applied at a network firewall, traffic management system, at the web server, in the application itself, in intrusion detection systems or in log analytical software, or in many of these. These are difficult to manage and in time there will be many IP addresses that no-one knows why they are allowed unless they are carefully documented, and subject to a fixed time limit when they are confirmed again by an appropriate person or removed. These extra addresses are quite often hard for someone else to guess.

However, there is another area where IP addresses are added to "allow lists", and this is for remote monitoring and testing services. These might be checking uptime, response times, content changes, HTML validation or security testing. The service providers publish the IP addresses of the source systems so that companies can specifically allow access to their web sites. Since the number of these services is relatively small, it's not too difficult to find which one might give access to areas of a web site or web application that the public (and malicious people) should not be able to get to. The particular danger here is that the IP addresses might be excluded from monitoring and logging, and therefore even a diligent web site manager might not realise for example the uptime monitoring service is making unusual, or excessive, requests.

Although it is not likely a malicious person is using this "trusted" address unless routing has been compromised as well, problems can go undetected, from what might seem to be a legitimate source. The IP address may have been typed incorrectly, or worse, the restrictions/exceptions may not have been implemented correctly allowing more addresses to have the privileged access than intended. Not logging a user's session is privileged access.

Allow traffic through, but be very specific what is allowed and monitor what's going on. Review all the exceptions periodically. Be especially careful about anything that bypasses authentication (such as allowing a search engine to crawl restricted-access content) on an otherwise public site.

Posted on: 29 September 2009 at 10:18 hrs

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More Entries

Trust : Web Security, Usability and Design
http://www.clerkendweller.com/trust
ISO/IEC 18004:2006 QR code for http://clerkendweller.com

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