One of the common ways of securing your system is by making the /tmp filesystem unable to run executables. This prevents users from executing scripts in /tmp which is generally writable by everyone.

You can restrict this with the mount option noexec.

Here is an example:

[[email protected] playground]# mount | grep play  
/dev/mapper/vgfirst-lv_test1 on /var/tmp/playground type ext3 (rw)  
[[email protected] playground]# ./helloworld.sh   
Hello World  
[[email protected] playground]# mount -o remount,noexec /dev/mapper/vgfirst-lv_test1 /var/tmp/playground  
[[email protected] playground]# mount | grep play  
/dev/mapper/vgfirst-lv_test1 on /var/tmp/playground type ext3 (rw,noexec)  
[[email protected] playground]# ./helloworld.sh   
-bash: ./helloworld.sh: Permission denied