The Bagle family of worms, fairly dormant for the past few months, has
spawned a flurry of variants that are kicking up a storm in the wild.
Several new versions of the Bagle worm have been released onto the
Internet in the past few weeks, bringing new life to the Bagle family of
worms, which had been quiet since late in February. They also are
spreading successfully and receiving medium to severe threat ratings
from anti-virus vendors.
”It just goes to prove that old tricks still work,” says Ken Dunham,
director of malicious code at iDefense, Inc., a security intelligence
company based in Reston, Va. ”The variants are having good success in
the wild and that’s disturbing. After all this time, everybody knows
about attachments and they know about security, but this worm is still
spreading. That’s disturbing.”
Steve Sundermeier, a vice president at Central Command, an anti-virus
company based in Medina, Ohio, says they have logged in Bagle-AE,
Bagle-AF, Bagle-AG, Bagle-AH and Bagle-AI. The worm’s author or authors
dropped the worm’s source code into two of the recently released
variants, feeding other virus writers who may want to write and release
their own Bagle variant.
Some security analysts speculate that the Bagle author, trying to avoid
prosecution, was copying the creator of the MyDoom worm family when he
released the source code. By distributing the source code to thousands
or even hundreds of thousands of machines, the author could more easily
try to deny responsibility for any worm code found on his machine.
But regardless of his strategy, the release of the source code could
mean a run of Bagle variants is on its way.
”We expect to see many new Bagle variants in the months to come,” says
Dunham. ”Once the source code has been made available, it’s easy to
make new variants and distribute them.”
And the new variants, though not as wide spread and disruptive as their
earlier siblings, are still causing problems.
Bagle-AI, which was first seen in the wild just a few days ago, garnered
a medium-threat ranking and spread rapidly. Sundermeier says, though,
that the variant slowed down on Tuesday and the ranking has been dropped
to a low-to-medium threat.
The Bagle variants are mass-mailing worms that also can spread over file
sharing applications. They arrive with .exe, .ser and .zip files
attached. Once they have a foothold in a computer, the worms search out
anti-virus and personal firewall applications and shut them down. Some
of the variants also try to connect to a German Web site to download
modifications to itself. A backdoor is opened in the compromised
computer so spam or other viruses can be sent without the owner’s
knowledge or consent.
When Bagle first hit the scene this winter, it caused a lot of problems.
Variant after variant hit the wild when the worm author got into a
spitting contest with the Netsky author. The worm war that ensued
between the two created a disruptive series of attacks on the Net.
The alleged author of the Netsky worms was arrested in Germany this
spring, and most security analysts thought that would bring an end to
the string of variants from both Netsky and Bagle.