[ISN] Hackers don't time exploits for maximum impact, researcher says

From: InfoSec News (alerts@private)
Date: Sun Jul 01 2007 - 22:28:30 PDT


By Gregg Keizer
June 29, 2007 

The idea that cybercriminals stockpile exploits, then time their release 
to do the most damage gives them too much credit, a security researcher 
said today.

"We think that [attackers are] all highly skilled and doing careful 
planning," said Craig Schmugar, a security researcher at McAfee Inc. 
"It's not always the case."

Schmugar compared the disclosure date of 200 zero-day vulnerabilities 
affecting Windows against the nearest monthly Microsoft Corp. patch day 
to find out if there was anything to the idea of "Exploit Wednesday" -- 
the supposed hacker practice of releasing exploits immediately after the 
release of regularly scheduled security updates from Microsoft on the 
second Tuesday of each month.

Under the Exploit Wednesday concept, attackers dispense threats right 
after a patch day to maximize the window of vulnerability, figuring that 
they have at least 30 days before Microsoft releases the next round of 

There doesn't seem to be much to the idea, said Schmugar. "I don't see 
Exploit Wednesday as a strategically timed release, but that it comes 
about simply because more information is being made available," he said. 
Some hackers parse Microsoft's vulnerability disclosures for enough 
information to put them on an exploit track, Schmugar said, while others 
reverse-engineer an attack after comparing the patched files with their 
vulnerable predecessors.

The data doesn't prove that's what happens, Schmugar acknowledged, but 
it did discount the idea that all hackers are patient, intelligent and 
lucky enough to strategically launch their exploits right after a patch 

In 2005, for example, 18% of the zero-day threats were disclosed within 
a three-day period either side of Patch Tuesday; a normal distribution 
for that week-long span would be 23%, Schmugar pointed out. During 2006, 
31% were within three days of patch day; so far this year, 24% fall 
within the range. "The data suggests that at least in 2005 and 2007 
strategic releases were not that common," Schmugar said. "Even 2006 only 
showed an 8% deviation."

Hackers have to weigh any attempt at attack timing against the 
possibility that the zero-day vulnerability will be discovered, and 
patched, before they can launch it, said Schmugar. "It's like trying to 
sell stock at its peak price. Yes, attackers could potentially hold 
their vulnerabilities, but they could also shoot themselves in the foot 
by doing that."

Interestingly, a follow-up analysis hinted at a better chance that 
attackers do hoard the most valuable vulnerabilities -- those originally 
reported as able to execute remote code. Of that zero-day subset, 41% of 
these most critical vulnerabilities were disclosed within three days 
either way of Patch Tuesday in 2006, and 30% so far this year, for a 
deviation of 18% and 7%, respectively.

Even here, however, Schmugar was suspicious, since the dates associated 
with active exploits are inherently inaccurate. "We don't always know 
right away of a zero-day vulnerability or exploit," said Schmugar. "I've 
been privy to information that showed by the time a patch was released, 
the attack had existed two or three weeks."

Schmugar was hesitant to stake out a conclusion because the data could 
be interpreted more than one way. "I'm somewhere in the middle between 
thinking attackers are and are not strategically launching exploits. 
Generally, though, because of the risk that their vulnerabilities will 
be found, I don't believe they think it's even worth it to hold one."

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