A worm, which takes advantage of a six-month-old vulnerability in SQL Server, is having a significant effect on Internet performance this weekend.

The SQL Slammer Worm uses SQL Server Resolution service buffer overflow flaw dating from last July to commandeer vulnerable servers. These serve as drones which randomly scan for more vulnerable servers and fire out exploit code.

Although Slammer is not destructive to an infected host (like Code Red it only exists in memory), it
generates a damaging level of network traffic when it scans for additional targets. The worm continuously sends 367 bytes of exploit and propagation code across port 1434/UDP until the SQL Server process is shut down. Unlike Nimda these attacks are not directed towards local sub-nets but spread across the wider Internet.

ISP UUNET is experiencing critical latency and Level 3 severe latency, according to Internetpulse.net, as Slammer zombies fire off bandwidth crunching chunks of useless traffic.

Military.com report five of the 13 root DNS servers are down, with up to 10 experiencing "massive packet loss" due to the DDoS effect the worm creates.

Fortunately, infected servers are relatively easy to cure, once identified. Admin need only take infected servers offline, apply Microsoft's patch, and restart their machines to cleanse them of infections.

Security firm also recommend blocking port 1434/UDP at firewalls or ISP's routers to stop Slammer's scans getting through.

Fixing the problem is the most important task in hand for now. But after the dust has settled it might be instructive for Redmond to explain why it implemented such a poorly thought out 'ping'-like feature on SQL Server 2000, which has become the root cause of significant security problem this weekend. ®

External Links

SQL Slammer Worm advisory by security tools firm ISS
More on the vulnerability it exploits from its discoverers Next Generation Security Software