Date: 10 May 2002 18:44:15 -0000
From: Christian decoder Holler <christian_holler@web.de.>
To: [email protected]Subject: Flaw caused by default rulesets in many desktop firewalls under windows
Several Desktop-Firewalls for Windows, such as Tiny
Personal Firewall 2.0 or ATGuard, maybe also others, allow
DNS resolving by default. That allows reversed trojans to
connect to a server on port 53 and send/receive commands
and informations without the user knowing it. The firewall
permits any communication to any server on port 53 UDP. I
wrote a small trojan in VB and tested it with Tiny Personal
Firewall 2.0 and it worked.
Solution: Change the default rules for DNS to a fixed host,
for example to the DNS server of the ISP or the DNS server
in the local network.
cu
Chris (decoder)
