PayPal Password-stealing Trojan Mass Mailed

Several million copies of a password-stealing Trojan horse were spammed to Internet users late last week, a security company said Monday, and workers returning to the office who open the attachment risk a computer kidnapping.

U.K.-based BlackSpider Technologies said that it had already intercepted more than 3.2 million messages with an attached Trojan, and claimed that it took 52 hours for the first anti-virus vendor to issue a signature that detected and deleted the malware.

Clagger.h, as Sophos dubbed it (Symantec named it "PWSteal.Tarno.s"), comes with the subject head of "Notification: Your Account Temporally Limited," and targets PayPal users. The associated e-mail claims that PayPal has detected unusual activity on the recipient's PayPal account. If the user opens the attached file, Clagger.h silently installs.

Not only does Clagger.h set a backdoor so the attacker can later add more malicious code to the PC, but it lurks in the background and nabs usernames and passwords from any window or Web page with text strings ranging from "cash" and "bank" to "log" and "id."

"This Trojan horse has been aggressively seeded, using spam technology, to distribute malicious code to as many vulnerable computers as possible, in the shortest amount of time," said Graham Cluley, a Sophos senior technology consultant, in a statement.Astute users will be waved off by a gaffe in the spam's subject heading.

"A simple spelling mistake in the subject line should alert innocent recipients that this isn't a genuine message from PayPal," he added. In the message, the word "Temporarily" is misspelled as "Temporally," although its conceivable that the hacker was trying to tell users that their PayPal password was limited by materialistic or ephemeral qualities. Or not.

"People should always think carefully before running unsolicited code on their computer," Cluley advised.