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Last week’s sophisticated bot attack against Windows installations of the MySQL database engine has fizzled after DNS (Domain Name System) service authorities shut off access to IRC servers controlling the worm.

The bot, which launched brute-force attacks on weak MySQL passwords, was infecting vulnerable systems at the rate of 100 per minute.

At its peak, the SANS Internet Storm Center reported that about 8,500 hosts were connected to the IRC (Internet Relay Chat) server to retrieve propagation instructions. However, once access to those servers was denied, the spread of the worm stopped.

But Johannes Ullrich, chief technology officer at the SANS Internet Storm Center, warned that a serious threat remains. “In the past, we’ve seen botnets move from server to server, so it won’t be surprising to see another attack soon.”

“These bots are written with different attack modules. It simply means someone could write a different module to connect to a different server to launch new attacks,” Ullrich told on Monday.

Because the bot takes advantage of weak passwords, Ullrich again urged database administrators to strengthen security policies for firewalls and passwords.

Administrators also should set up restricted access to root accounts and apply firewall rules to make sure MySQL servers are not exposed to attackers, he added.

MySQL AB, the Cupertino, Calif.-based company that develops and manages the program, also released a security alert spelling out the effects of the worm.

“There are two basic steps to protect your MySQL Servers: Always use strong passwords on all accounts, [and] use firewalls to protect your MySQL servers,” the company said.

MySQL is a freely available database engine designed to provide fast access to stored data. It is installed on more than 8 million systems worldwide.

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