Last week, Google announced an additional tier of user security notification in its search results. Sites which Google believes have been hacked or otherwise compromised, but do not yet host malware may be marked with "This site may be compromised" on search engine result pages.
This status is not as severe as notifying users that the site hosts malware, when "This Site May Harm Your Computer" is displayed, but take it as an important warning. Compromise often leads to malware hosting. See my previous post about suggestions on to prepare for such an event — these are identical for "This site may be compromised".
Google may also remove sites completely from its indexes and search results. This could be due to not having access, content such as malware, incorrect use of the robots exclusion standard, incomplete site maps, incorrect HTTP status codes, or other reasons that lead to a breach of its webmaster guidelines. Sites may also be removed or excluded due to legal action (e.g. if Google receives a Cease and Desist Notice - examples).
There is another tier which doesn't really fit in the above diagram — sites which use common application software which is out-of-date or which is known to contain security vulnerabilities, may receive WebMaster Tools messages, but this information is not currently displayed to search engines users.
Remember, just because Google has not detected use of old/vulnerable application software, or detected compromise or detected malware, this doesn't mean these none of these are true. Verify your own web applications, and have a plan in place in case any of these occur. Oh, and make someone accountable.
Posted on: 21 December 2010 at 09:00 hrs