Updates to the HL1 Engine have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:
HL1 Engine
Fixed several exploits triggered by malicious server operators (found by Stan Bubrouski)
As part of the next version of VAC, which is currently in testing, the Linux game server now must have GLIBC 2.3.2 or above installed
HL1 Engine Master Server Query Protocol These changes bring the HL1 engine's querying protocol in line with that of the Source engine. If you connect to Steam enabled game servers using a third party tool, you may need to contact the vendor for an update.
Added a challenge number to A2S_PLAYER and A2S_RULES server queries. Setting "sv_enableoldqueries" to 1 (currently the default) allows old style (no challenge/response) queries to work
Changed A2S_INFO server query to require the string "Source Engine Query" appended to the end of the query packet
Removed support for "info", "infostring", "details", "players" and "rules" queries, use A2S_INFO, A2S_PLAYERS and A2S_RULES instead
