This OCTET STRING is the fourteenth of up to fifteen event-specific variable slots on a Windows event trap, one of the additional positions the MIB says are only filled by platform variants using the fuller 16-variable event format, such as Windows Server 2003's logon-failure event versus XP's 11-variable version. An admin should not expect this slot to be populated when polling an XP-era source. On a Server 2003 trap it might carry a transited-services string related to the logon.