[ISN] New Domain Poisoning Attacks Microsoft Servers

InfoSec News isn at c4i.org
Thu Apr 7 02:16:06 EDT 2005


By Gregg Keizer 
TechWeb News 
April 6, 2005 

The DNS cache poisoning that first struck more than a month ago and
led to users being redirected from popular Web sites to malicious
sites that infected their machines with spyware, is continuing, said
the Internet Storm Center (ISC) Wednesday. The attacks are taking
advantage of vulnerabilities and design flaws in Microsoft server

DNS cache poisoning occurs when an attacker hacks into a domain name
server, one of the machines that translate URLs such as
www.techweb.com into the appropriate IP address. The attacker then
"poisons" the server by planting counterfeit data in the cache of the
name server. When a user requests, say, techweb.com, and the IP
address is resolved by the hacked domain server, the bogus data is fed
back to the browser and the user is directed to another Web site, not
the intended destination.

To highlight the danger, the ISC raised its Homeland Security-esque
alert color code from Green to Yellow. According to ISC, Yellow
represents that "we are currently tracking a significant new threat.  
The impact is either unknown expected to be minor to the
infrastructure. However, local impact would be significant."

To set the DNS cache poisoning threat in perspective, Yellow is the
same alert color code that ISC used during the SQL Slammer, MSBlast,
and Sasser worm outbreaks, three of the nastiest in the last two

The newest attack, said Kyle Haugsness, one of the ISC analysts, is
actually the third since March 4. Like the initial attack, the
motivation is certainly money, since the result is again the
installation of mass quantities of spyware on victims' PCs.

"The motivation for these attacks is very simple: money," Haugsness
said. "The end goal of the first attack was to install spyware/adware
on as many Windows machines as possible."

The second attack, he continued, "seems to have been launched by a
known spammer," said Haugsness. That second attack, which took place
starting March 24, redirected users from legit sites to sites selling
prescription drugs.

Initially, Haugsness and the other ISC analysts thought that a DNS
cache poisoning attack was beyond the skills of most spammers -- and
so might be proof that the original attackers were contracting their
services, but now he said "they might be completely unrelated. In
fact, one of the things we discovered after looking into these attacks
is just how easy they are to carry off."

The third, and still-ongoing attack, which began March 25, has the
same goal -- install spyware -- as the first, said Haugsness. One of
the DNS servers involved in the early-March attack wasn't cleaned up
properly, and the attacker returned and changed the poisoning tool.

"Right now this is still going on," said Haugsness. "The attackers are
changing IP addresses around and poisoning other DNS servers [to stay
ahead of security authorities]."

Among the domains included in one of the poisoned DNS servers during
the first attack were major sites such as americanexpress.com,
cnn.com, redhat.com, and msn.com. "These [665] domains organizations
did not have their DNS cache's poisonedthese organizations were not
compromised, although it is possible that customers of these sites
unknowingly gave out login information or personal information to the
malicious servers," wrote Haugsness in a long report posted on the ISC
site about the attacks.

Although there's essentially nothing an end-user can do to protect
him- or herself -- other than to regularly sweep the system for
spyware and/or have real-time anti-spyware defenses up and running --
DNS server administrators, particularly those in enterprises, should

Windows-based DNS servers are particularly vulnerable, since Windows
NT Server 4.0 and Windows 2000 Server prior to SP3 are insecure
against DNS cache poisoning attacks. Windows 2000 Server SP3 and
later, as well as Windows Server 2003, are configured securely by
default. (For more information, see this Microsoft Knowledgebase
article. [1])

Other users that are vulnerable are those running various Symantec
gateway security products who haven't patched bugs the Cupertino,
Calif.-based vendor released in mid-March.

But the entire Windows server software platform -- including properly
configured NT/2000 and 2003 systems -- seems to have an architectural
design flaw, said Haugsness, that makes them vulnerable to cache
poisoning attacks. He said ISC was working with Microsoft to pin down
the exact cause.

"This is a lot easier to do than we thought," said Haugsness, who
noted that cache poisoning isn't new. "That's the main reason we went
out there with this, and bumped up to Yellow.

"What's scarier is that this could be used in lot more subtle fashion,
to make it difficult, or even impossible to detect."

[1] http://support.microsoft.com/default.aspx?scid=kb;en-us;241352

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