ISPs report success in fighting malware-infected PCs

Computers infected with malicious software remain a big headache for ISPs, but two companies have designed systems that have made the problem much more manageable.

When a PC gets infected with malicious software, it's often used for sending spam. It makes the ISP look bad as well as sucking up bandwidth, making networks more congested.

True Internet, one of Thailand's largest ISPs, had been hit by an ever-increasing number of malware-infected computers on its network. The spam and malware traffic was so severe that its customers -- most of whom are still on dial-up connections -- were complaining of slow speeds, said Tanapon Chadavasu, head of True Internet's network operations.

The problem was also costing the company money, since bandwidth is expensive in the area, and more hardware was needed to keep the network running, Chadavasu said during a presentation Wednesday at the Messaging Anti-Abuse Working Group Meeting in Amsterdam.

True Internet installed equipment from a New Zealand company called Esphion that identifies anomalous behavior on the network. The passive devices identify attack patterns, such as denial-of-service attacks or zero-day worms.

If Esphion's sensors detect something, such as a high amount of spam, an alert is sent to a controller, which can then automatically quarantine the subscriber, Chadavasu said.

If a subscriber then goes online, they are redirected to page that notifies them that their computer may be infected. True Internet has a partnership with security vendor Trend Micro to scan subscribers' PCs.

"Once they have cleaned the computer ... we will allow them to get back on the 'Net," Chadavasu said.

True Internet used to only quarantine a customer after two bad incidents were detected, but changed its policy last August to quarantine after one incident, Chadavasu said. Spam on its network dropped dramatically, and customers' Internet security improved.

Close to 70 percent of the PCs that have been quarantined once or twice are never quarantined again, Chadavasu said, which points to better security awareness among consumers.

"We think it's very effective," Chadavasu said.

NetCologne, an ISP and cable and phone provider in Germany, has taken a similar approach to automating how it deals with subscribers infected with malware.

NetCologne also locks down subscribers that appear to be engaged in some sort of abuse and gives them an opportunity to download Microsoft security patches or even purchase security software, said Dietmar Braun, a system engineer and developer for the company. Once users have cleaned their system and applied patches, they can automatically unblock their access.

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