Colleges and universities have come under attack by Storm Worm botnets following attempts to detect infections through vulnerability scanning, a response centre for academic networks stated last week.
The Research and Education Networking Information Sharing and Analysis Centre (REN-ISAC) sent out the warning last Thursday following "numerous incidents" and advised school information technology managers to respond quickly to any infection on their networks.
The Storm Worm's distributed denial-of-service (DDoS) attacks appear to strike back at the network of any computer that scans an infected system, REN-ISAC officials said in the advisory.
"The attacks have been ICMP (Internet Message Control Protocol), can last more than a day, involve a large number of sources scattered globally, and can yield very significant attack traffic," the advisory warned. "With the impending return of students for fall classes, the DDoS-the-scanner-when-scanned behavior represents a significant risk for the EDU sector."
The advisory is the latest warning regarding the Storm Worm, which first started spreading in January using fairly large, but controlled, bursts of email routed through previously compromised computers.
Each burst typically sends out a custom variant, trying to infect systems before the user updates their anti-virus definitions. The program compromises systems by luring their users into opening the attachments of messages with subject lines regarding news events, including violent storms in Europe - a characteristic that led to the program's naming.
The control exercised by the online criminal group seeding the program makes the Storm Worm's name a misnomer; the malicious software is not a worm, as it does not spread automatically, but a bot program. Because it relies on deception to infect target systems, security experts have also referred to the program as a Trojan horse.
Over the past seven months, the Storm Worm's methods have evolved. The program, which is responsible for sending a significant portion of the stock pump-and-dump spam seen on the internet, has used tensions in the Mideast as bait for its malicious hook and has varied the type of attachments used to hold its fraudulent advertisements.
The program has also adopted a technique known as fast-flux Domain Name Service (DNS) hosting to make it harder to take down the botnet.
The botnet created by the Storm Worm has also grown significantly. From January to the end of May, SecureWorks detected a total of 2,815 bots trying to send email to the company's clients. Between the beginning of June and the end of July, the cumulative number of internet addresses trying to send spam jumped to 1.7 million, averaging about 100,000 addresses each day.