Critical vulnerability was discovered in Symantec Internet Security 2005, posible afected products: Symantec Personal Firewall 2005, Symantec Internet Security 2004, Symantec Personal Firewall 2004,  Symantec Personal Firewall 2003, Symantec Internet Security 2006, Symantec Personal Firewall 2006.

Defective program feature allows to establish remote connections undetected - thus creating a perfect exploit for trojans and hacker activities. Symantec products generally have a rule "Default outbound NetBIOS", allowing programs to establish direct IP connections on ports 137, 138, 139. Therefore, trojan programs can undetectably bypass Symantec firewall and connect on these ports to attacker's remote server. However, resolving IP from DNS will be detected by the firewall.

Solutions:
- Disable "Default outbound NetBIOS" rule
- Modify "Default outbound NetBIOS" rule and restrict connections only to LAN

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DimichSoft Security Group
http://www.dimichsoft.com/security.html