Phages use anti-CRISPR proteins (Acrs) to counteract the bacterial CRISPR-Cas systems. Here, the authors characterize AcrIF24, which functions as an Aca (Acr-associated) to repress and regulate its own transcription, dimerizes the Csy complex, blocks the hybridization of target DNA, and tethers non-sequence-specific DNA to the Csy complex.