Web.com has merged the SnapNames and NameJet inventories. So when you do a search for NameJet, SnapName domains will show up, and vice versa.
Buy Security (Computers) Expired Domains
List of Expired domains in the Security (Computers) Niche
I've tried a number of expired domain finding tools and services but the support from DomCop is second to none. It's in my top two of tools to use, and the best I've used for crawling.Glen Allsopp, Gaps.com