Hanson, 31, has spent the last six seasons with the Philadelphia Eagles, totaling 239 tackles, 2.5 sacks and all four of his career interceptions while primarily playing in a nickel corner role in 91 games.
Financial terms of Hanson's contract with the Raiders were not disclosed.
Scheduled to earn $825,000 in base salary, the Eagles released Hanson as part of their cuts down to a 53-man roster to avoid having his salary fully guaranteed. According to a source with knowledge of Hanson's terminated contract, the veteran could have earned an additional $300,000 in incentives.
The 6-foot-1, 187-pound Van Dyke saw his draft stock soar after running a 4.28 40-yard dash at the 2011 NFL Scouting Combine. Van Dyke started four of 14 games as a rookie, playing in less than 30 percent (27.91 percent) of the Raiders' defensive snaps, according to official playing-time documents.
Van Dyke's struggles with consistency during the preseason landed him on the roster bubble, but his combination of size and speed should result in an opportunity elsewhere this season.
UPDATE: The Raiders confirmed Hanson's signing later Monday.
Follow Brian McIntyre on Twitter @brian_mcintyre.