A fake email notice that purports to come from the Internal Revenue Service is continuing to make the rounds, widely ramping up attacks against businesses and individuals, according US-CERT.
The attacks are concealed in a bogus email containing a subject line of ‘Notice of Underreported Income,'" according to a US-CERT advisory posted Monday.
The email typically contains a link or an attachment that, if opened, will infect users with the Zbot/Zeus trojan, a nasty credentials-stealing program that seeks to compromise banking login information.
The fake IRS notification emails have been in circulation for the past few weeks, according to security researchers at PandaLabs.
“We've monitored the situation closely and have observed 30 active domain names currently spreading the Zeus trojan affiliated with the spam campaign, as well as 300 links used in the attack over the past month,” wrote Sean-Paul Correll, PandaLabs threat researcher, on the PandaLabs blog.
The Zbot/Zeus trojan is particularly pernicious, experts said. Even having an up-to-date anti-virus product only protects PCs against it 23 percent of the time, according to internet security firm Trusteer. The trojan has sophisticated morphing and rootkit mechanisms that enable it to operate deep within the operating system, and it's coded to protect itself from detection and removal.
"There's no end in sight for this," Correll told SCMagazineUS.com Tuesday. "Every time the good guys get close to fixing it, the bad guys come out with another version."
The IRS said it does not discuss personal matters over email.
“The IRS does not initiate taxpayer contact via unsolicited email or ask for personal identifying or financial information via email,” the IRS says in a warning to taxpayers.