AS/400 Telnet 5250 terminal emulation clients, as implemented by (1) IBM client access, (2) Bosanova, (3) PowerTerm, (4) Mochasoft, and possibly other emulations, allows malicious AS/400 servers to execute arbitrary commands via a STRPCO (Start PC Organizer) command followed by STRPCCMD (Start PC command), as demonstrated by creating a backdoor account using REXEC.