What is it ? 
HLDSGUARD is a Half-Life dedicated server addon 
which protects a server from following attacks of hackers.  
Here actual at this time attacks list for Half-Life 
servers : 
1. Hlboom 
2. CSDOS 
3. Pigface DoS 
 
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Features: 
    * Attackers Loging(incl. IP , Attack Type, Date) 
    * Autobaning 
    * Announcing attackers 
More about This: 
http://www.awakelgcc.narod.ru