Scammers use Symantec, DNS holes to push adware

Scammers use Symantec, DNS holes to push adware

Online scam artists are using a weakness in DNS and in some Symantec security products to distribute spyware and adware to unsuspecting Web surfers.

Online scam artists are manipulating the Internet's directory service and taking advantage of a hole in some Symantec products to trick Internet users into installing adware and other annoying programs on their computers, according to an Internet security monitoring organisation.

Customers who use older versions of Symantec's Gateway Security Appliance and Enterprise Firewall are being hit by DNS (Domain Name System) so-called poisoning attacks. The attacks cause Web browsers pointed at popular Web sites, such as, and, to go to malicious Web pages that install unwanted programs, according to Johannes Ullrich, chief technology officer at The SANS Institute's Internet Storm Center (ISC). The attacks, which began on Thursday or Friday, may be one of the largest to use DNS poisoning, Ullrich said.

Symantec issued an emergency patch for the DNS poisoning hole on Friday. The company did not immediately respond to requests for comment Monday.

The Domain Name System is a global network of computers that translates requests for reader-friendly Web domains, such as, into the numeric IP (Internet Protocol) addresses that machines on the Internet use to communicate.

In DNS poisoning attacks, malicious hackers take advantage of a feature that allows any DNS server that receives a request about the IP address of a Web domain to return information about the address of other Web domains.

For example, a DNS server could respond to a request for the address of with information on the address of, or, even if information on those domains was not requested. The updated addresses are stored by the requesting DNS server in a temporary listing, or cache, of Internet domains and used to respond to future requests.

In poisoning attacks, malicious hackers use a DNS server they control to send out erroneous addresses to other DNS servers. Internet users who rely on a poisoned DNS server to manage their Web surfing requests might find that entering the URL of a well-known Web site directs them to an unexpected or malicious Web page, Ullrich said.

Some Symantec products, such as the Enterprise Security Gateway, include a proxy that can be used as a DNS server for users on the network that the product protects. That DNS proxy is vulnerable to the DNS poisoning attack, Symantec said Friday in an article on its Web site. Symantec's Enterprise Firewall Versions 7.04 and 8.0 for Microsoft's Windows and Sun Microsystems' Solaris have the DNS poisoning flaw, as do versions 1.0 and 2.0 of the company's Gateway Security Appliance, Symantec said. (See:

Internet users on some networks protected by the vulnerable Symantec products had requests for Web sites, such as directed to attack Web pages that attempted to install the ABX toolbar, a search toolbar and spyware program that displays pop-up ads, Ullrich said.

The DNS poisoning attacks were easy to detect because Web sites involved in the attack do not mimic the sites that users were trying to reach, Ullrich said. However, DNS poisoning could be a potent tool for online identity thieves who could set up phishing Web sites that are identical to sites like or, but secretly capture user information, he said.

Some of those customers told ISC that they installed a patch that the company issued in June to fix a DNS cache poisoning problem in many of the same products, but were still susceptible to the latest DNS cache poisoning attacks, according to information on the ISC Web site.

Ullrich does not believe that Symantec's customers are being targeted, just that they are susceptible to attacks that are being launched at a broad swath of DNS servers.

The ISC is collecting the Internet addresses of Web sites and DNS servers used in the attack and trying to have them shut down or blacklisted, ISC said.

Symantec customers using one of the affected products are advised to install the most recent hotfixes from the company, Ullrich said.

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