Up to 40,000 Web sites have been hacked to redirect unwitting victims to another Web site that tries to infect PCs with malicious software, according to security vendor Websense.
Those Web sites have likely been hacked via a SQL injection attack, in which improperly configured Web applications accept malicious data and get hacked, Leonard said.
Another possibility is that the FTP credentials for the sites have somehow been obtained by hackers, giving them access to the inner workings of the site. It appears the hackers are using automated tools to seek out vulnerable Web sites, Leonard said.
The latest campaign underscore the success hackers have at hosting dangerous code on poorly secured Web sites.
Once a user has been directed to the bogus Google analytics site, it redirects again to another malicious domain.
That site tests to see if the PC has software vulnerabilites in either Microsoft's Internet Explorer browser or Firefox that can be exploited in order to deliver malware, Leonard said.
If it doesn't find a problem there, it will launch a fake warning saying the computer is infected with malware and tries to get the user to willingly download a program that purports to be security software but is actually a Trojan downloader, Leonard said. Those fake security programs are often called "scareware" and don't work as advertised.
As of last Friday, only four of 39 security software programs could detect that Trojan, although that's now likely changed as vendors such as Websense swap malware samples with other companies in order to improve overall Internet security.
It's not clear what the hackers are doing with the newly compromised PCs, although it's possible they can be configured to send spam, become part of a botnet or have data stolen from them.
The malicious domain serving up the malware is hosted in the Ukraine, the same region where notorious Russian Business Network (RBN) operated.
RBN is a gang of cybercriminals involved in phishing campaigns and other malicious activity, Leonard said. That Web site appeared to be down as of Tuesday afternoon. The RBN is thought to be inactive now.
"Whether this is a part of that group or whether it's a copycat using some of the techniques that are similar to those used by the malware group in the past we are not quite certain yet," Leonard said. "It is very difficult to pinpoint the exact people behind this."
Since so many Web sites have been hacked to deliver the attack, it's nearly impossible to contact them all, Leonard said.
Websense said the latest attacks don't appear to be related to Gumblar, a malware campaign under way last month.
Gumblar resulted in at least 3,000 Web sites getting infected with malicious code that scanned users' computers for vulnerabilities in Adobe Systems software.
Once on a PC, Gumblar steals FTP log-in credentials, using that information to help spread to other computers. It also commandeers a person's Web browser and replaces Google search results with other dangerous links.