Although this post is by the League of Legends account, this will also affect Teamfight Tactics players. Here is the support page that confirms it.

Vanguard is Riot’s anti-cheat software that was originally made for the release of VALORANT, and is now coming to League of Legends. They did not note a specific patch in the article, but will most likely be here in about a month.

For more information about Vanguard and why they chose to add it to LoL, check out their dev article.