One way to defeat a multi-level security solution is to leak data via

A 'bypass regulator' is not a recognized technical term or attack technique in security literature.

Steganography hides data within carrier files such as images, but it is a concealment technique rather than a method that exploits unintended communication paths to defeat MLS information flow controls.

A covert channel is a communication mechanism that was not intended to exist in the system design, allowing information to be transferred in ways that circumvent mandatory access controls enforced by MLS solutions. Because MLS policies only govern intended channels, covert channels - such as timing channels or storage channels - can leak data across security boundaries undetected. This is the classic attack vector specifically studied in the context of defeating MLS architectures.

Asymmetric routing describes a network condition where traffic takes different paths in each direction, which is a routing anomaly and not a technique used to leak data past MLS security boundaries.