McAfee has become the first hardware supplier to use a new technique that it claims can protect companies from the threat of botnet-launched distributed denial-of-service (DDoS) attacks.
DDoS attacks typically use armies of hijacked PCs to target a server or Wan link with large amounts of incomplete SYN packets from false addresses, which are difficult to stop if the system cannot separate them from legitimate traffic or identify the source.
Unlike conventional DDoS detection systems, which rely on statistical analysis of traffic, the first layer of the new Advanced Botnet Protection (ABP) intrusion-prevention system (IPS) uses a proxy to pass or block packet traffic dependent on whether or not it is ‘“complete’.
Many IPS systems also track the number of attempts at connection, but this can be overwhelmed if specifically targeted by an attacker. A sophisticated attack like this - flooding servers with non-legitimate ACK or acknowledgement packets generated in response to SYN traffic - is dealt with by the ABP using an established encryption scheme used in the Linux environment, called SYN cookies.
The new protection module was rolled out in December as a free software upgrade to all subscription customers of the IntruShield intrusion prevention appliances.
Any new technique that can prevent the march of the botnets has to be welcomed. It would be tempting to say even isolated attacks would be preferable to the rather sinister hijacking of an army of PCs.