How did trojan bypass my security countermeasures?
 

Hi, My desktop is running XP Pro SP3 and has McAfee A/V protection installed: [Security Center 9.15, Virus Scan 13.15, Personal Firewall 10.15. Anti Spamware 10.15] CPU Intel x86 PC with 4Gb main memory running on 945HCM-S mother board BIOS American Megatrends P1.00 08/19/2008