Iwuh's deal, which ESPNChicago.com first reported would happen, was for the veteran minimum of $630,000.
A four-year veteran, Iwuh played four years in Jacksonville after signing with the club as an undrafted free agent in 2006. The Jaguars released Iwuh in April, and the Bears brought him in last week for minicamp on a tryout basis.
The club offered Iwuh a contract Sunday before he left Halas Hall, a league source told ESPNChicago.com, but it couldn't make the deal official until it released Brock, who spent the last six weeks of the 2009 season on the Bears practice squad.
The Bears envision Iwuh as a four-phase special-teams contributor initially, but there's a chance he could earn a role as a reserve linebacker. Playing in 58 career games with three starts for the Jaguars, Iwuh tallied 61 special-teams tackles, which ranks third in franchise history, in addition to 64 tackles on defense, a forced fumble and a fumble recovery.
Iwuh played in 15 games last season for the Jaguars with two starts, producing a career-high 38 tackles and two tackles while finishing second on special teams with 17 tackles.
Michael C. Wright covers the Bears for ESPNChicago.com.