Troj_Strat.GI is a Trojan that arrives as an attachment to email messages spammed by another malware or a malicious user.

It accesses a certain Web site to download and execute a file, which Trend Micro detects as WORM_STRAT.GI. As a result, routines of the downloaded worm are also exhibited on the affected system.

Technical details can be found at this Trend Micro page.