The cache feature of search engine is a useful feature that allows you to access a website even if it has been taken offline or removed completely from the internet.
Security firm Aladdin has reported that an attack on a university originated from a 'poisoned cache'; it was an infected page that had been taken offline for a certain amount of time, but survived in a search engine cache.
Although the name of the search engine was not revealed, it could only be one of the big three: Microsoft, Google or Yahoo.
More worrying is the fact that the difference in URL (the cached pages have Google's URL), mean that traditional list-based URL filtering systems cannot weed out those pages.
Depending on whether the cached page is popular or not, the malicious code could remain online for months, infecting even more web users.
Legally, the search engines could be liable to prosecution because they have become the largest 'legitimate' source of storage for malicious code.
A simple solution could be for Google to look for strings of malicious code within their cache and remove them as they are found.