Towards understanding and improving forensics analysis processes, in this work, we conduct a complex experiment in which we systematically monitor the manual forensics analysis of live suspected infections in a large production university network that serves tens of thousands of hosts. In particular, over a period of 4 weeks, we manually investigate, in coordination with the IT department of our university, 200 security incidents about compromised hosts detected by an IDS alert correlator. The security investigation combines data from four security sources: (1) Snort alerts, (2) reports from four scanning and vulnerability assessment tools, (3) five independent blacklists, and (4) a search engine (Google).