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.