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Unix find tutorial

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Part 6: Finding SUID/SGUID files

Unix permissions model SUID attribute Principle of Least Privilege chmod command  

Suid root refers to a special attribute called set user id. This attribute allows the program to do functions not normally allowed for owner of the file to perform.

Low level networking routines, controlling graphical display functions, changing passwords, and logging in are all examples of programs that rely on executing their functions as a user that is not restricted by standard file permissions. While many programs need this functionality, the program must be bug free in only allowing the user to do the function the program was designed for. Every SUID root program represents a potential security problem.  Attempts of rogue users to install SUID programs in thier home directories are best blocked by using nosuid mounting option for /home partition.

The first step in controlling SUID root programs is to have a baseline, the list of all SUID program in the system. This can be achieved quite easily by using find:

find / -type f \( -perm -4000 -o -perm -2000 \) -exec ls -lg {} \; 2>/dev/null >suidfiles.txt

Or it you are interested only in files owned by root:

find / -type f  -user root \( -perm -4000 -o -perm -2000 \) -exec ls -lg {} \; 2>/dev/null >suidfiles.txt


  1. This will find both set user id and set group id programs.
  2. Please note that this program does not detect all SUID programs available on the system, there might be directories perversely set to permissions 000
  3. Attempts of rogue users to install SUID programs in their home directories are best blocked by using nosuid mounting option for /home partition.
  4. Solaris used to have a script called fix-modes written by Casper Dik that changed permission in a more reasonable, secure set. Such script can be created for any OS. For example on most modem systems it does not make sense to preserve SUID attribute uucp and similar "never used" programs.
  5. Most modern Unixes block usage of SUID attribute on shell scripts.

Above command is using GNU find and executes ls command. You can use option -ls instead but output will be slightly different. Solaris POSIX find command is different:

find / -type f \( -perm -4000 -o -perm -2000 \) -exec ls -l {} \; 

This command will find all the SUID programs on a system and pipes the commands to a file called suid.list. The next step in controlling SUID root programs is to analyze which programs should not be SUID root or can be removed without impeding system functionality. An obvious example of something that should not be SUID root is /usr/X11R6/bin/SuperProbe.  This is a program merely used for testing purposes.

'chmod -s /usr/X11R6/bin/SuperProbe'

Other programs that are unneeded to be SUID root include anything in the svgalib  hierarchy. This library itself is buggy and nothing that depends on it should be SUID root in a secure system.

Here is an example of minimized suid.lst though perhaps a little too overzealous. For example, the functionality that does not exist with this setup is ability to use ping and traceroute by a regular users and this is close to a security paranoia. It can be compensated by controlling access to those program via sudo.

But in any case minimization of the number of SUID program is task worth trying. It is excessive zeal that hurts...

See also

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Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers :   Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism  : The Iron Law of Oligarchy : Libertarian Philosophy


War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda  : SE quotes : Language Design and Programming Quotes : Random IT-related quotesSomerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose BierceBernard Shaw : Mark Twain Quotes


Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 :  Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method  : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law


Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds  : Larry Wall  : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOSProgramming Languages History : PL/1 : Simula 67 : C : History of GCC developmentScripting Languages : Perl history   : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history

Classic books:

The Peter Principle : Parkinson Law : 1984 : The Mythical Man-MonthHow to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Haterís Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite

Most popular humor pages:

Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor

The Last but not Least

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