Page "VA-111 Shkval" Paragraph 3

Announced as being deployed in the early 1990s, although previously operational as early as 1977, the Shkval is designed as a countermeasure against torpedoes launched by undetected enemy submarines.

It may also be used as a counter to incoming torpedoes whereby it is launched at the enemy submarine, forcing it to evade, and hopefully cutting the guidance wire to its own torpedo in the process.