By Robert Lemos
15th October 2006
Analysis -- On December 1, 2005, two email messages were sent from a
computer in Western Australia to members of two different human rights
organizations. Each email message carried a Microsoft Word document with
a previously unknown exploit that would take control of the targeted
person's computer and open up a beachhead into the group's network.
The attack failed, as did a second attempt to infiltrate the same
human-rights groups a week later, due in no small part to an
overabundance of caution on the part of email security provider
MessageLabs, which initially blocked the emails based on the strangeness
of the Word attachments. The attacks only targeted a single person at
each organization and, after the two attempts, never repeated.
Such targeted Trojan horse attacks are quickly becoming a large concern
for corporations, the military and political organizations, said
MessageLabs security researcher Alex Shipp. The email security provider
intercepted 298 such attacks between May 2005 and May 2006, and the
threat of targeted Trojans is only increasing.
"If you haven't noticed these attacks and you are a big company, you
have likely already been attacked," Shipp told attendees at the Virus
Bulletin 2006 conference. "Your problem is no longer how do I avoid
being attacked, but how do I find where I've been compromised."
Targeted Trojan horse attacks are quickly becoming a major issue for the
antivirus and computer-security industries. Last year, computer
emergency response groups in the UK, Canada and Australia warned of such
attacks. While the United States Computer Emergency Readiness Team
(US-CERT) did not issue a warning, security firms confirmed at the time
that US government agencies and companies had already been targeted by
such malicious software.
A major problem for large companies, government agencies and other
potential targets is that antivirus software is not good at stopping
low-volume attacks aimed at single companies. Traditional antivirus
programs detect widespread attacks based on matching to a known pattern
and do not fare well against low-volume Trojans. And even when they do
detect such attacks, the larger volume threats are inevitably moved to
the top of the firms' to-do lists, because they affect a larger number
of customers, said antivirus industry insiders.
"There is no value whatsoever in having signature-based antivirus when
facing a targeted attack," said Joshua Corman, host protection architect
for Internet Security Systems (ISS). "We, the AV industry, haven't
turned the corner in being able to detect these attacks consistently."
If a company misses the initial attack, the results can be costly,
Corman said. He pointed to an example of one company, a pharmaceutical
firm, that got infiltrated by a targeted Trojan attack. The company only
realized it had been compromised when some valuable data was encrypted
and the key held for ransom. The company had to pay and, after the
incident, spent a month cleaning the compromised systems from its
offices in three countries. Corman would not name the company, which
became ISS client after the incident.
While MessageLabs might detect tens of thousands of copies of a typical
mass-mailing computer viruses in a single day, the company is finding,
at most, ten targeted Trojans a week, Shipp said. According to the data
collected by MessageLabs, more than half of the 298 attacks detected
over 12 months consist of a single email sent to a single person at a
company. In total, 1,344 emails were sent during the period studied by
Shipp. Military agencies, human rights organizations and pharmaceutical
companies are some of the types of groups that are being targeted by
specifically aimed attacks.
The attacks are also very well researched, Shipp said. One targeted
Trojan was sent to five employees at one company - every single person
was a member of the firm's research and development team.
"The bad guys have done their homework," Shipp said.
During the 12 months studied by Shipp, the majority of the Trojan horse
programs, almost 70 per cent, used a malicious Word document as the
vehicle for the attack. That's already changing, with PowerPoint and
Excel documents now becoming popular, he said. The one type of document
that oddly is not being used by attackers is the PDF format of Adobe
Shipp added that most companies cannot just block the problematic
attachments, even if they realize the threat.
"In many cases, even if the company is vulnerable, .doc files are their
lifeblood, so they can't block Word documents," Shipp said.
Most of the attacks come from the Pacific Rim, emanating from Internet
addresses in mainland China, Hong Kong, Australia and Malaysia. However,
one IP address that consistently attacks military installations comes
from a computer in California. Shipp believes that the computer could
have been compromised as part of a botnet.
In fact, Shipp believes that three major groups are involved. The first
and largest group is the most active and uses a variety of different
tactics, but most commonly uses a zero-day exploit in the attack. The
researcher believes it is also possible that this group could be several
independent actors. He feels more confident about the other two groups:
One targets only Hong Kong companies with an attack once every three
weeks or so, and the other attacks military sites from a computer in
California about every two weeks.
The attack data underscores an overall trend in threats. While some
hobbyist virus writers undoubtedly still exist, most malware is now
written for profit.
"No one other than the kids want to infect a million people anymore,"
said Graham Cluley, senior technology consultant for antivirus firm
Sophos. "You would rather deal with 50 or 100 systems at a time."
Sophos and other security companies are adopting better versions of
behavioral blocking software to combat the threat. Traditional
behavioral blocking stops a program that attempts a specific action, a
technique that frequently flags legitimate programs as potential
threats. Sophos instead characterizes programs by a collection of
actions attempted by the program in a virtual sandbox and blocks the
executable if the actions seems malicious. Called "behavioral genotype
protection" by Sophos, the technique has already caught a number of
targeted and low-volume attacks, Cluley said.
However, the antivirus industry is still moving too slowly, ISS's Corman
said. The Trojan horse sold to private investigators by an Israeli
couple took 18 months to detect.
"People in the industry keep talking about the Israeli Trojan horse,
because that is one of the few public examples," Corman said. "But
that's just one of hundreds, if not thousands, of successful attacks."
This article originally appeared in Security Focus.
Copyright 2006, SecurityFocus
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