Attack code released for new DNS flaw

Hackers have released software that exploits a recently disclosed flaw in the Domain Name System (DNS) software used to route messages between computers on the Internet.

The attack code was released Wednesday by developers of the Metasploit hacking toolkit.

Internet security experts warn that this code may give criminals a way to launch virtually undetectable phishing attacks against Internet users whose service providers have not installed the latest DNS server patches.

[ Related reading: With DNS flaw now public, attack code imminent ]

Attackers could also use the code to silently redirect users to fake software update servers in order to install malicious software on their computers, said Zulfikar Ramizan, a technical director with security vendor Symantec. "What makes this whole thing really scary is that from an end-user perspective they may not notice anything," he said.

The bug was first disclosed by IOActive researcher Dan Kaminsky earlier this month, but technical details of the flaw were leaked onto the Internet earlier this week, making the Metasploit code possible. Kaminsky had worked for several months with major providers of DNS software such as Microsoft, Cisco and the Internet Systems Consortium (ISC) to develop a fix for the problem. The corporate users and Internet service providers who are the major users of DNS servers have had since July 8 to patch the flaw, but many have not yet installed the fix on all DNS servers.

[ Related reading: Details of major Internet flaw posted by accident ]

The attack is a variation on what's known as a cache poisoning attack. It has to do with the way DNS clients and servers obtain information from other DNS servers on the Internet. When the DNS software does not know the numerical IP (Internet Protocol) address of a computer, it asks another DNS server for this information. With cache poisoning, the attacker tricks the DNS software into believing that legitimate domains, such as idg.com, map to malicious IP addresses.

In Kaminsky's attack a cache poisoning attempt also includes what is known as "Additional Resource Record" data. By adding this data, the attack becomes much more powerful, security experts say.

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