A Trojan horse dubbed "South Park'' that made its first appearance on the internet last June is on the loose again, antivirus software vendors warned on Friday.
The Trojan spreads by sending itself as an email attachment to all the addresses listed in a user's Outlook Express program. It attempts to do this every 30 minutes, and has the potential to cause storms of email that can clog up a company's network, the vendors said.
The attachment contains an icon of the character Kyle from the cult cartoon series "South Park", and will appear as though it has come from someone known to the recipient, vendors said.
The Trojan has been reported on Windows NT and 9x machines at dozens of large corporations, government organisations, universities and internet companies, primarily in the US but also in Asia and Europe, said Martin Skov, a product marketing manager with Network Associates' McAfee software division.
Known as W32/Pretty.worm.unp, the Trojan is a variant of the W32/PrettyPark.worm that first surfaced last June and has been dormant for the most part ever since. The new variant differs in that it is not compressed, which made it a little harder to detect initially, Skov said.
The Trojan may also try to connect to an internet relay chat server, and could potentially use the connection to get information such as the computer name and registered owner, as well as dial up networking and user names stored on that computer, Skov said. Network Associates hasn't received a report of that happening yet, he added.
While its payload isn't considered too severe, in the sense that it doesn't delete data, antivirus vendors upgraded their rating on the Trojan on Thursday from medium to high risk, primarily because of its ability to spread quickly and clog networks. Network Associates received 70 reports of it in the first four days of the week, compared with 150 reports in the prior two-week period. It was first discovered it in mid-February.
"It's not limited to one industry sector; it's hit pretty much across the board," Skov said.
The number of reports subsided somewhat on Friday and Network Associates hopes to downgrade it to medium risk soon, Skov said. Network Associates has classified seven Trojans and viruses as high risk in the past year, he added.
Outlook Express users should be aware of emails that carry the subject line, "C:/coolprogs/prettypark.exe." File attachments are called "Pretty park.exe" and in some cases "Pretty~1.exe."
Network Associates said it posted a cure for the Trojan at its McAfee AVERT site at http://vil.nai.com/vil/wm98500.asp/. Consumers can find protection and further information at McAfee.com's site at http://www.McAfee.com/.