Search engine spammers have ramped up their efforts to ensnare the unwary, according to a report released Wednesday by MessageLabs, a messaging security company.
Search engine spam accounted for 17% of spam in January. During this period, spam from previously unknown bad sources accounted 73.4% of e-mail, or 81.1% of e-mail if about 7.6% of messages from known spam sources were included.
MessageLabs chief security analyst Mark Sunner said that search engine spam is rising but could not immediately provide historical data for comparison.
Search engine spam, not to be confused with Web spam, is similar to a phishing message in that it begins with a Web link in an e-mail message.
"Search engine spam is a technique that allows the spammer to include a link constructed from a search engine query in an e-mail message," MessageLabs explains in its January report. "When followed, the link will resolve in the spammer's forged Web site. This means that the spammers can send messages without directly mentioning the spam Web site, which makes it difficult for traditional anti-spam products to detect the malicious link."
Unlike phishing links, search engine spam can take advantage of special parameters found only in search query URLs. Google, for example, supports the BtnI parameter. This is associated with the "I'm Feeling Lucky" button, which sends the person clicking on the button directly to the Web site associated with the top search result for the given query, without first loading the standard Google search results page.
By using this parameter, a spammer can construct a URL that looks like it points to Google, but will take anyone clicking on it one step further, to the top-ranked site for the query. If a spammer has not managed to manipulate Google to present his or her site as top result for the query, adding the inURL parameter accomplishes the same result. This parameter restricts the search spam query to a single site, which guarantees the top result, the one to which the searcher is automatically and unluckily redirected, is the spammer's malicious site.
"Google works hard to preserve the quality of our index," a Google spokesperson said in an e-mailed statement. "We actively identify sites that serve malware or abuse our quality guidelines in other ways. Sites that exploit browser security holes to install software (such as malware, spyware, viruses, adware, and Trojan horses) are in violation of our quality guidelines and may be removed from Google's index. The same is true for spam. We regularly remove spammers from our index."
Last November, Google removed tens of thousands of malicious Web pages from its index. The company will almost certainly continue to do so periodically for the foreseeable future. It's likely that Google will eventually curb such abuse; other companies like eBay have already taken steps to prevent similar URL redirection tricks.
Sunner of MessageLabs also noted a rapid rise in the number of targeted phishing attacks. Many of these, he said, are directed at C-titled executives. In 2005, MessageLabs detected two attacks per week involving targeted Trojans out of 1.5 billion messages. In 2006, it found one such attack per day out of 180 million messages. In May 2007, it saw 10 targeted attacks per day out of 250 million messages. In November 2007, it was seeing 924 targeted attacks every five hours.
Sunner attributes rapid growth of such attacks to the appearance of phishing toolkits. He predicted that the pollution of communication channels with malware will force Internet service providers to become more involved in network-level filtering. "Users are starting to question their ISPs' role in all this," he said, likening the situation to a poisoning of the water supply. "If you got botulism from your water provider, you'd probably take it up with them."