Botnet is deemed the most dangerous threat, and has posed terrible impact in many aspects. The information security software named “Personal Computer Security Guard” (PCSG) can guarantee browsing security and prevent PC from being a zombie. The test data on unknown virus detection says that PCSG gets 95% detection rate on contrast to that of 16.7% ~ 27.3% of commercial anti-virus software. In addition, PCSG is easy to use and free of charge, so we can expect its popularization on PCs. The impact of the botnet will be dramatically reduced if PCSG is extensively deployed on PCs.