A new worm-like threat is spreading on the Internet and targeting computers running the MySQL open source database software. Thousands of Windows machines running MySQL have been infected, according to one security expert.

The new pest is a version of a common network worm named "Forbot." It infects machines by exploiting loosely secured MySQL installations running on Windows machines connected to the Internet. The new Forbot variant is one of the first known examples of an automated Internet threat targeting MySQL, and could infect machines running a wide range of database applications that use MySQL, according to Joe Stewart, a senior security researcher at LURHQ Corp.

MySQL is an open source database software program that is a popular alternative to Microsoft's closed source SQL Server database among Web developers. The MySQL AB Web site claims more than 5 million MySQL installations worldwide.

MySQL AB did not immediately respond to a request for comment.

The new threat was first detected Wednesday, when Web developers in Australia reported infections by a program called "spoolcll.exe," which was attempting to connect to an IRC channel in Sweden, according to Johannes Ullrich, chief technology officer at TThe SANS Institute's Internet Storm Center (ISC).

ISC also noted a spike in scans for MySQL port 3306, which is associated with infection by the new Forbot variant, Ullrich said.

A check of the IRC channelshowed more than 8,000 systems connected, though many more MySQL systems could be infected, but prevented from connecting by the overwhelmed IRC server, Ullrich said.

The new version of Forbot infects machines by taking advantage of administrator accounts with weak or nonexistent passwords. The worm cracks the accounts by trying values from a pre-defined list of around 1,000 possible passwords, Ullrich said.

First discovered in July, Forbot is a network worm with built-in back door features, according to anti-virus company Sophos PLC. Dozens of different Forbot variants have been identified.

Once the worm gains access to the MySQL root account, it uses a known exploit called the MySQL UDF Dynamic Library Exploit to upload and install malicious code to the infected system. The exploit used by Forbot was first noted in December, and allows an attacker with so-called "root" administrator permissions to expand the default functions available to the root account dynamically, Stewart said.

"I'm not even sure it's an exploit so much as a feature - the ability to create new functions on the fly," he said.

Systems infected with the new Forbot variant connect to an IRC channel that is controlled by the worm author and receive instructions through that channel, Stewart said.

Right now, the systems are being instructed to scan for and infect other MySQL systems, but those instructions could be changed to instruct the infected systems to launch a denial of service attack, or other actions, which would stop the worm's spread, at least temporarily, he said.

To be infected, MySQL has to be configured to allow the root account to log in remotely to the system. By default, the root account is only allowed to log on at the machine running MySQL, rather than remotely. The root account also has to use a password that is on Forbot's list of passwords, Ullrich said.

The worm poses the most risk to Web developers who may be running the product on loosely secured workstations that are connected to the Internet but do not have firewall software running, he said.

However, MySQL is commonly used in third party database-driven applications, as an inexpensive and open source alternative to Microsoft SQL. That could expand the pool of likely victims beyond the developer community to "power users," Stewart said.

Stewart said that the new Forbot variant will probably not rate a severe threat, noting that the number of computers running MySQL is much smaller than the number systems running programs like Windows or Microsoft Office.

However, the worm is notable for being one of the first automated attacks on MySQL, Ullrich and Stewart said.

MySQL administrators were encouraged to strengthen their root account password, make sure that MySQL does not allow remote logins for the root account and use a firewall to prevent direct access to port 3306 from the Internet.