TMOUT and TIMEOUT are environmental setting that activate the timeout of a shell. The value is in seconds. TMOUT=n - Sets the shell timeout to n seconds. A setting of TMOUT=0, or unset TMOUT disables the automatic session timeout. readonly TMOUT- Both export and lock TMOUT environmental variable to it's present value, preventing unwanted modification during run-time. Rationale: All systems are vulnerable if terminals are left logged in and unattended. The most serious problem occurs when a system manager leaves a terminal unattended that has been enabled with root authority. In general, users should log out anytime they leave their terminals. You can force a terminal to log out after a period of inactivity by setting the TMOUT and TIMEOUT parameters in the /etc/profile file. The TMOUT parameter works in the ksh (Korn) shell, and the TIMEOUT parameter works in the bsh (Bourne) shell. Impact: This recommendation is set at Level 2 (using readonly). The recommendation - at Level 1, would use export instead.
Solution
Review /etc/profile to verify that TMOUT is configured to: include a timeout of no more than 900 seconds to be readonly verify readonly statement is the last statement /usr/bin/egrep -n -e 'TMOUT|TIMEOUT' /etc/profile This should return something similar to: 40:# TMOUT=120 41:TMOUT=900 42:TIMEOUT=900 43:readonly TMOUT TIMEOUT If either setting is missing, and/or the readonly statement, add these to /etc/profile. Default Value: TMOUT=0