SAV Scan Engines

Over on the MyItForum AV email discussion list, a couple of the regulars reported older versions of Symantec Antivirus (pre version 9) had problems detecting some gaobot varients.
I wondered how this could be. I know that SAV 9 is configured to start earlier that previous versions. This was done to protect against some specific malware tricks. Is this the extra protection they are referring to or do older versions of SAV not get the scan engine upgrades.
Symantec has two types of scanning engines. Security Response AV engines are released throughout the year via liveupdate and intelligent updates. This updates virus detection techniques in the virus defs. You can look at the file properties to see the current version number on the engine binaries (naveng.sys, navex15.sys, navex32a.dll, naveng32.dll).
The Scanning Engine version number that you see in the UI refer to the properties of the navapi32.dll file. This file is involved with boot scanning functionality in the product. This is updated only with new builds of the file not with virus definitions.
Symantec KB DocID: 2002080609215348