Personal Firewalls Spring Security Leaks - Update

[InfoSec News <isn () c4i org>]

http://www.newsbytes.com/news/01/171949.html

By Brian McWilliams, Newsbytes
ALISO VIEJO, CALIFORNIA, U.S.A.,
07 Nov 2001, 12:08 PM CST
 
Software firewalls deployed by millions of PC users offer only
"illusory" protection against Trojan horses and other malicious
programs, security experts warned today.

Techniques for defeating the outbound data filters in popular personal
firewalls such as Zone Alarm and Norton Personal Firewall have been
independently posted on the Web by several researchers. Using the
methods described, a rogue program could upload private user data
without being detected by the firewall, the experts claim.
 
To evade a firewall's guards against unauthorized data leaks, the new
techniques include commandeering a legitimate program such as
Microsoft's Internet Explorer and forcing it to send out data on
behalf of the attacker.

"If a firewall is going to allow some program to transmit and receive
data over the Internet, and that program allows other programs to
control its actions, then there's no point in blocking anything at
all," wrote Bob Sundling in text accompanying the source code of
TooLeaky, a firewall test program he developed to demonstrate the
problems.

FireHole, a similar testing tool, also has been made available on the
Web by its author, Robin Keir, lead network security programmer with
Foundstone, a computer security consulting firm. Both TooLeaky and
FireHole sneak past personal firewalls and upload harmless test data
to an external site.

According to Gregor Freund, chief operating officer for Zone Labs,
FireHole exploits a known security flaw in Windows referred to as
SetWindowHookEx, which allows an application to insert code into
another program.

Freund said that Zone Labs will release an update to Zone Alarm next
week that will provide limited protection against the bug on Windows
NT, 2000, and XP systems. A more complete fix will be incorporated in
the next full release of Zone Alarm, version 3.0, which is due in
January.

Freund said users can easily defeat the technique used by TooLeaky by
configuring Zone Alarm to require Internet Explorer to ask permission
every time it accesses the Internet.

Keir told Newsbytes that other techniques are likely to be discovered
for defeating outbound filtering, and that the development suggests
that blocking leaks is "a race the firewall makers will never win."
Nonetheless, Keir said he still believes personal firewalls are
valuable for their ability to block incoming attacks.

A third firewall test utility, YALTA, creates a virtual device driver
that sends data to any Internet address without being detected by
firewalls, according to a description of the program, which stands for
Yet Another Leak Test Application.

The new firewall testing utilities represent a second generation of
such programs, building upon a tool developed by Gibson Research Corp.
After GRC president Steve Gibson released LeakTest a year ago to
highlight what he called "internal extrusion" flaws in personal
firewalls, many vendors made changes to improve the outbound filtering
techniques used in their firewall products.

Product manager Tom Powledge told Newsbytes that Symantec was studying
the new firewall bypass techniques and would likely revise Norton
Personal Firewall to defend against them. But Powledge noted that
computer users require anti-virus software and safe computing
practices to prevent rogue programs from establishing a beachhead.

"Once a hacker has code running on your computer, they have a
tremendous amount of power. We've always said that effective Internet
security is a combination of tactics," said Powledge.

The firewall leak discoveries come the same week as an independent
testing agency announced the results of its first certification tests
of personal firewalls. ICSA Labs said three products passed its
battery of tests, which included "restriction of outgoing network
communication."

All three of the ICSA certified products, Zone Alarm, Norton Personal
Firewall, and Tiny Software's Tiny Personal Firewall, can be defeated
by the new outbound attacks in some circumstances, according to the
authors of TooLeaky and FireHole. An ICSA representative said the firm
was still testing the new tools and had no immediate comment.

More information on FireHole is at http://keir.net/firehole.html .

The TooLeaky home page is at http://tooleaky.zensoft.com .

YALTA is available at
http://www.soft4ever.com/security_test/En/index.htm .

Gibson's LeakTest site is at http://grc.com/su-leaktest.htm .

ICSA's Personal Firewall certification page is at
http://www.icsalabs.com/html/communities/pcfirewalls/cert_prods.shtml



-
ISN is currently hosted by Attrition.org

To unsubscribe email majordomo () attrition org with 'unsubscribe isn' in the BODY
of the mail.