Beware the Pulsing Zombies

DDoS attacks with devilish twist

Virus Bulletin Distributed denial of service attacks, one of the most difficult security risks to guard against, could become even harder to detect with the development of tools that turn agents on and off during an attack.

So called 'pulsing zombies' (which sounds like something from the Night of the Living Dead) will be difficult to detect as they will not be always active, making the isolation and removal of malware from infected machines even harder.

Also, users may not even notice they are subject to such an attack, because it would result in service degradation, not outright failure.

Pulsing Zombies

Alexander Czarnowski, chief executive of Polish security firm Avet, told the Virus Bulletin Conference in Prague today that viruses that drop pulsing zombies on vulnerable boxes can be expected as DDoS tools evolve.

He singled out Doser, a Windows virus, that carries a ping flood as its payload, and the Sadmind worm, which affects Unix boxes, as examples of the direction that virus writers are taking. Email-borne worms could become used in DDoS attacks too.

Intrusion detection systems (IDS), and egress filtering (to drop outgoing packets with a false IP address) at the router level can help, but are not a complete solution to the problem. For one thing IDS set-ups can themselves become subject to DDoS attacks via tools such as Stick.

Czarnowski's presentation re-emphasised the importance of detecting DDoS components on hosts because just a few compromised boxes, carrying agents that bounce attacks off reflector servers to disguise their origin, can have a disproportionately large effect.

The possible emergence of 'pulsing zombies' make disinfection more important than ever, especially since there's little sign (or hope) of a complete solution to DDoS attacks. ®

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