The new version of the attack just appeared Thursday afternoon, and while details are still sketchy, experts say its main purpose is to install a back door on compromised PCs. Users victimized by the attack receive an e-mail or an instant message containing a link directing them to a malicious Web page.
The page is being hosted by a number of different sites, all of which share common "whois" information and appear to be deliberately serving the page, according to Thor Larholm, senior security researcher at PivX Solutions LLC, based in Newport Beach, Calif. The Trojan also will change the start page of the infected PC.
Once a user clicks on the link, the Web server attempts to download the back door. Larholm said a PC running a fully patched copy of Windows XP and Internet Explorer 6 will be compromised by the new version of Download.Ject, as will machines running older version of Windows and IE.
But machines running SP2 (Service Pack 2) for XP are not vulnerable to the new attack. Larholm added that the vulnerabilities exploited in this attack have been known for some time.
"It doesnt use any unknown flaws," he said. "But its not at automated as it could be. I think its still evolving. But this clearly has a financial motivation behind it."
The original version of the attack surfaced in late June, and experts said the servers being used to compromise client machines had themselves been compromised and pressed into service.
This time around, the attackers have been able to place their code on a variety of servers, apparently with the owners knowledge. Some of the sites serving the malicious code are porn sites, and others are advertising servers, Larholm said.
The earlier version of Download.Ject was used to monitor outgoing Web traffic to capture passwords and user IDs for online banking sites and other sensitive data.