Sept. 11 turned Sung-Ki Lim and Sang Jun from geeks to G-men. Well, they’re still geeks, but instead of pursuing an MBA or traveling far and wide as systems analysts, the two men are putting their technical skills to work for the FBI. As computer crime increases and as terrorists increasingly use digital technology to plot their activities, law enforcement finds that it needs to recruit from the same fields that high-tech headhunters have been plowing for years…