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Index: U

U.S. Department of Energy : F.3.4.12. France: universities, Ministry of Research and Education in France, CNRS, CEA, INRIA, CNES, INRA, IFREMER, and EDF

U.S. Department of the Navy : F.3.4.44. U.S. Department of the Navy

U.S. law : (see laws)

U.S. Secret Service

26.2.2. Federal Jurisdiction
F.3.3. U.S. Secret Service (USSS)

UDP (User Datagram Protocol)

16.2.4.3. UDP
17.1.3. The /etc/inetd Program
(see also network services)
packet relayer : E.4.15. UDP Packet Relayer

ufsdump : (see dump/restore program)

UIDs (user identifiers)

4.1. Users and Groups

4.1.2. Multiple Accounts with the Same UID

real versus effective

4.3.1. Real and Effective UIDs
C.1.3.2. Process real and effective UID

RPC requests and : 19.2.2.2. AUTH_UNIX

su command and : 10.1.2.1. su command and /etc/utmp and /var/adm/wtmp files

of web servers : 18.2.1. The Server's UID

zero : (see root account; superuser)

UK Defense Research Agency : F.3.4.37. UK: Defense Research Agency

ulimit command : 25.2.5. Soft Process Limits: Preventing Accidental Denial of Service

Ultrix : 1.3. History of UNIX

trusted path : 8.5.3.1. Trusted path
UUCP : 15.4.1.3. Format of USERFILE entry without system name

umask

5.3. The umask
5.3.2. Common umask Values
8.4.3. Finding Dormant Accounts

unattended terminals

12.3.5. Unattended Terminals
12.3.5.2. X screen savers

uninterruptable power supply (UPS)

2.2. Risk Assessment
12.2.1.1. Fire

Unisys : F.3.4.39. UK: other government departments and agencies

universes : 5.9.1. Dual Universes

UNIX : 1. Introduction

add-on functionality of : 1.4.3. Add-On Functionality Breeds Problems

conventional passwords : 3.2.6. Conventional UNIX Passwords

DAC (Discretionary Access Controls) : 4.1.3. Groups and Group Identifiers (GIDs)

DNS under : 16.2.6.1. DNS under UNIX

encryption programs for

6.6. Encryption Programs Available for UNIX
6.6.3.6. PGP detached signatures

filesystem

5. The UNIX Filesystem
5.10. Summary

history of : 1.3. History of UNIX

modems and

14.5. Modems and UNIX
14.5.3.3. Privilege testing

networking and : 16.1.2. Networking and UNIX

operating systems : (see operating systems)

primary network services

17.3. Primary UNIX Network Services
17.3.23. Other TCP Ports: MUDs and Internet Relay Chat (IRC)

process scheduler : C.1.3.3. Process priority and niceness

processes : (see processes)

programming references : D.1.11. UNIX Programming and System Administration

published resources for : D.1. UNIX Security References

security and

1.4. Security and UNIX
1.4.3. Add-On Functionality Breeds Problems

signals : C.3. Signals

starting up

C.5. Starting Up UNIX and Logging In
C.5.3. Running the User's Shell

Version 6 : 1.3. History of UNIX

viruses : (see viruses)

web server on : 18.2. Running a Secure Server

unlinked files : 25.2.2.7. Hidden space

unowned files : 24.4.1.8. Unowned files

unplugging connections : 24.2.5. Getting Rid of the Intruder

unpredictability of randomness : 23.6. Tips on Generating Random Numbers

upgrades, logging : 10.7.2.1. Exception and activity reports

uploading stored information : 12.3.4. Protecting Local Storage

UPS (uninterruptable power supply)

2.2. Risk Assessment
12.2.1.1. Fire

uptime command : 8.1.3. Accounts That Run a Single Command

urandom device : 23.7.4. Other random number generators

Usenet

17.3.13. Network News Transport Protocol (NNTP) (TCP Port 119)
E.2. Usenet Groups
(see also NNTP)
cleanup scripts : 11.5.3. Abusing Automatic Mechanisms
encryption for : (see ROT13 algorithm)
posting breakins to : 24.6. Resuming Operation
reporting security holes on : 2.5.1. Going Public

User Datagram Protocol (UDP) : 16.2.4.3. UDP

user error : 7.1.1.1. A taxonomy of computer failures

user IDs : (see UIDs)

USERFILE file (UUCP)

15.4.1. USERFILE: Providing Remote File Access
15.4.2.1. Some bad examples

usermod command

-e option : 8.4.3. Finding Dormant Accounts
-f option : 8.4.3. Finding Dormant Accounts
-s option : 8.3. Restricting Logins

usernames : 3.1. Usernames

aliases for : 8.8.9. Account Names Revisited: Using Aliases for Increased Security

doubling as passwords (Joes) : 3.6.2. Smoking Joes

last command and : 10.1.3. last Program

as passwords : 8.8.3.1. Joetest: a simple password cracker

special

4.2. Special Usernames
4.2.3. Impact of the /etc/passwd and /etc/group Files on Security

using someone else's

4.3. su: Changing Who You Claim to Be
4.3.8. Other Uses of su

users

4. Users, Groups, and the Superuser

4.1. Users and Groups

4.1.2. Multiple Accounts with the Same UID

(see also groups; su command)

assigning passwords to : 8.8.1. Assigning Passwords to Users

auditing who is logged in

10.1.2. utmp and wtmp Files
10.1.2.1. su command and /etc/utmp and /var/adm/wtmp files

authentication for Web : 18.3.3. Setting Up Web Users and Passwords

becoming other

4.3. su: Changing Who You Claim to Be
4.3.8. Other Uses of su

checklist for : A.1.1.2. Chapter 3: Users and Passwords

dormant accounts and

8.4. Managing Dormant Accounts
8.4.3. Finding Dormant Accounts

identifiers for : (see UIDs)

importing to NIS server

19.4.1. Including or excluding specific accounts:
19.4.4.2. Using netgroups to limit the importing of accounts

letting in threats : 11.4. Entry

limited : 8.1.5.1. Limited users

logging

10.4. Per-User Trails in the Filesystem
10.4.3. Network Setup

NIS passwords for : 19.3.2.1. Creating passwords for users

nobody (Secure RPC) : 19.3.2.1. Creating passwords for users

notifying about monitoring : 26.2.6. Other Tips

proving identity of : 19.3.1.1. Proving your identity

recognizing as intruders

24.2. Discovering an Intruder
24.2.6. Anatomy of a Break-in

restricting certain : 18.3. Controlling Access to Files on Your Server

root : (see root account; superuser)

sending messages to : 10.5.1. The syslog.conf Configuration File

summarizing system usage by : 25.2.2.2. quot command

tainting : 18.2.3.4. Tainting with Perl

training : 13.2.1. Initial Training

UIDs : (see UIDs)

unattended terminals

12.3.5. Unattended Terminals
12.3.5.2. X screen savers

USERFILE entries for : 15.4.1.2. USERFILE entries for local users

www : 18.2.2. Understand Your Server's Directory Structure

users command

10.1.2. utmp and wtmp Files
24.2.1. Catching One in the Act

USG (UNIX Support Group) : 1.3. History of UNIX

/usr directory

4.3.7. The Bad su Log

(see also /var directory)

backing up /usr/bin : 7.1.2. What Should You Back Up?

/usr/adm directory : 11.5.3.6. Other files

/usr/adm/lastlog file : 10.1.1. lastlog File

/usr/adm/messages file : 10.2.3. messages Log File

/usr/bin directory

11.1.5. Viruses
11.5.1.1. PATH attacks

/usr/bin/uudecode : (see uudecode program)

/usr/etc/yp/makedbm program : 19.4.4.1. Setting up netgroups

/usr/lib/aliases file : 11.5.3.3. /usr/lib/aliases, /etc/aliases, /etc/sendmail/aliases, aliases.dir, or aliases.pag

/usr/lib directory : 11.5.3.6. Other files

in restricted filesystems : 8.1.5. Restricted Filesystem

/usr/lib/preserve program : 5.5.3.2. Another SUID example: IFS and the /usr/lib/preserve hole

/usr/lib/sendmail : (see sendmail)

/usr/lib/uucp/Devices file : 14.5.1. Hooking Up a Modem to Your Computer

/usr/lib/uucp directory

15.4.2.1. Some bad examples
15.5.2. Permissions Commands

/usr/lib/uucp/L-devices file : 14.5.1. Hooking Up a Modem to Your Computer

/usr/lib/uucp/L.cmds file : (see L.cmds file)

/usr/lib/uucp/L.sys file : 15.3.3. Security of L.sys and Systems Files

/usr/lib/uucp/Permissions file : (see Permissions file)

/usr/lib/uucp/Systems file : 15.3.3. Security of L.sys and Systems Files

/usr/lib/uucp/USERFILE file

15.4.1. USERFILE: Providing Remote File Access
15.4.2.1. Some bad examples

/usr/local/bin : 1.1. What Is Computer Security?

/usr/local/bin directory : 11.5.1.1. PATH attacks

/usr/local/etc/http/logs directory : 10.3.5. access_log Log File

/usr/local/lib directory : 11.5.3.6. Other files

/usr/sbin/rexecd : (see rexec service)

/usr/spool/cron/crontabs directory : 15.6.2. Automatic Execution of Cleanup Scripts

/usr/spool/uucp directory : 15.1.4. How the UUCP Commands Work

/usr/spool/uucppublic : (see uucppublic directory)

/usr/ucb directory : 11.1.5. Viruses

utility programs : 1.2. What Is an Operating System?

utimes commandn : 24.5.1. Never Trust Anything Except Hardcopy

utmp file

10.1.2. utmp and wtmp Files
10.1.2.1. su command and /etc/utmp and /var/adm/wtmp files
24.2.1. Catching One in the Act
24.2.4. Tracing a Connection

uucheck program : 15.5.3. uucheck: Checking Your Permissions File

uucico program

15.1.4. How the UUCP Commands Work
15.3. UUCP and Security
15.5.1.1. Starting up

uucp (user)

4.1. Users and Groups
4.2.2. Other Special Users

uucp command : 15.1.1. uucp Command

UUCP system

4.1.2. Multiple Accounts with the Same UID

14.5. Modems and UNIX

15. UUCP

15.9. Summary

additional logins : 15.3.1. Assigning Additional UUCP Logins

BNU

15.2. Versions of UUCP
15.5. Security in BNU UUCP
15.5.3. uucheck: Checking Your Permissions File

checklist for : A.1.1.14. Chapter 15: UUCP

cleanup scripts

11.5.3. Abusing Automatic Mechanisms
15.6.2. Automatic Execution of Cleanup Scripts

early security problems : 15.7. Early Security Problems with UUCP

HoneyDanBer (HDB) : 15.2. Versions of UUCP

logging : 10.3.4. uucp Log Files

mail forwarding : 15.6.1. Mail Forwarding for UUCP

naming computer : 15.5.2. Permissions Commands

over networks : 15.8. UUCP Over Networks

NFS server and : 15.3. UUCP and Security

passwords for : 15.3.2. Establishing UUCP Passwords

Taylor : 15.2. Versions of UUCP

over TCP : 17.3.20. UUCP over TCP (TCP Port 540)

Version 2

15.2. Versions of UUCP
15.4. Security in Version 2 UUCP
15.4.3. L.cmds: Providing Remote Command Execution

uucpa account : 15.3.1. Assigning Additional UUCP Logins

uucpd program : 15.8. UUCP Over Networks

uucppublic directory

15.1.1. uucp Command
15.4.1.3. Format of USERFILE entry without system name
15.5.2. Permissions Commands

uudecode program : 17.3.4.2. Using sendmail to receive email

uuencode program : 6.6.1.2. Ways of improving the security of crypt

uux command : 15.1.2. uux Command

- (hyphen) option : 15.1.2. uux Command
-r option : 15.1.4. How the UUCP Commands Work

uuxqt program : 15.4.1.3. Format of USERFILE entry without system name

uuxqtcmds files : 15.4.3. L.cmds: Providing Remote Command Execution

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