[2] During the early testing phase in 2002, some information was revealed about the program via the Half-Life Dedicated Server mailing lists.

Information on detected cheaters is sent to the ban list server on IP address 205.158.143.67 on port 27013,[10] which was later changed to 27011.

In July 2010, several players who successfully used information leaked from Valve to increase their chances of finding a rare Team Fortress 2 weapon called the Golden Wrench were banned by VAC.

[16][17] During the same month, approximately 12,000 owners of Call of Duty: Modern Warfare 2 were banned when Steam updated a DLL file on disk after it had been loaded into memory by the game, causing a false positive detection.

[18][19][20] In February 2014, rumors spread that the system was monitoring websites users had visited by accessing their DNS cache.

The system has been criticized for failing to detect LMAOBOX, a popular cheat program for Team Fortress 2, until May 2016, which resulted in a wave of bans.

[25] In February 2017, Valve announced plans to introduce a machine-learning approach to detecting cheats in Counter-Strike: Global Offensive, and that an initial version of the system was already in place, which would automatically mark players for manual detection by players through the "Overwatch" system.

[26] In March 2018, Valve publicized said machine-learning based approach in a talk at the Games Developer Conference, naming it VACNet.

AMD subsequently withdrew the driver update and Valve pledged to unban any affected users.

[28] Valve rarely discusses the software, as it may help cheaters write new code or conduct social engineering.

[21] The software sends client challenges to the machine; if the appropriate response is not received, it is flagged as a possible violation.

Whenever an anomaly is detected, an incident report is created and compared to a database of banned applications and/or analyzed by Valve engineers.

[47][48][49] Hovik "KQLY" Tovmassian, Simon "smn" Beck and Gordon "SF" Giry were banned shortly before they were scheduled to play at DreamHack Winter 2014.

[52] In March 2020, Elias "Jamppi" Olkkonen filed a lawsuit against Valve, alleging that a lifetime VAC ban negatively affected his esports career, specifically his inability to play in Valve-sanctioned Major tournaments, which subsequently prevented him from signing onto the esports team OG.