In Unix operating systems, internal field separator (abbreviated IFS) refers to the character or characters designated as whitespace by the operating system. IFS is actually a system variable, and it can be modified, which is useful programmatically in a number of ways. IFS typically includes the space and the newline.
Security Issues: This field can be manipulated by a hacker to help him in fooling the O/S to run another program in SUID mode to gain root access.
http://www.tech-faq.com/suid-root-script-binary.shtml
