According to Symantec security analyst Amado Hidalgo, a new Trojan horse called Infostealer.Monstres by Symantec has stolen more than 1.6 million records belonging to several hundred thousand people from Monster Worldwide Inc.'s job search service. That data is then used to target the Monster.com users with credible phishing mail that plants more malware on their machines.

"We are investigating the reports related to this Trojan and will take any necessary steps indicated by that investigation," Monster.com spokesman Steve Sylven said Sunday in an e-mail.

The personal information filched from Monster.com includes names, e-mail addresses, home address, phone numbers and resume identification numbers, said Hidalgo, who traced the data to a remote server used by the attackers to store the stolen information. Infostealer.Monstres ripped off Monster.com by using legitimate log-ins, likely stolen from recruiters and human resource personnel who have access to the "Monster for employers" areas of the site. Once inside, the Trojan horse ran automated searches for resumes of candidates located in certain countries or working in certain fields. The results were then uploaded to the attackers' remote server.

"Such a large database of highly personal information is a spammer's dream," said Hidalgo. In fact, that's exactly what the attackers are using their newly-acquired data for.

"The attackers first gather e-mail address and other personal information from resumes posted to Monster.com with Infostealer.Monstres," Hidalgo said. "Next, they will try to infect the computers of those candidates by sending targeted Monster.com phishing mails which install [Banker.c or Gpcoder.e]."

The first piece of malware, dubbed Banker.c by Symantec, is a run-of-the-mill information-stealing Trojan horse that monitors the infected PC for log-ons to online banking accounts. When it sniffs a log-on in process, Banker.c records the username and password, then transmits the data back to hacker HQ. Gpcoder.e, on the other hand, is "ransomware," the name given to Trojan horses that encrypt files on the hacked computer, then hold those files hostage until the user pays a fee to unlock the data.

Although both Banker.c and Gpcoder.e may be distributed in other ways -- SecureWorks Inc. last week said it had spotted something like the former coming from infected ads placed on job search sites -- Infostealer.Monstres' built-in mailing code and template lets it send messages posing as missives from Monster.com straight to the job-site users it finds in its automated searches.