Security - We will get there

Basics, important sites, HOWTO's, handbooks, hardening, tips

Checklists
UNIX Security Checklist v2.0: http://www.cert.org/tech_tips/unix_s...cklist2.0.html
SANS, The Twenty Most Critical Internet Security Vulnerabilities: http://www.sans.org/top20/
SANS SCORE Checklists for W32/Solaris/Cisco IOS/Mac OS/etc etc: http://www.sans.org/score/
SANS http://www.sans.org/infosecFAQ/linux/linux_list.htm
SANS, Reading room, Linux Issues: http://www.sans.org/rr/catindex.php?cat_id=32

Securing
CERT, Security improvements: http://www.cert.org/security-improvement/
CERT, Tech Tips: http://www.cert.org/tech_tips/
Linux Administrator's Security Guide (LASG): http://www.seifried.org/lasg/
Linux Security Administrator's Guide (SAG, old): http://www.tldp.org/LDP/sag/index.html
The Linux Network Administrator's Guide (NAG): http://www.tldp.org/LDP/nag2/index.html
Securing & Optimizing Linux: The Ultimate Solution (PDF): http://www.tldp.org/LDP/solrhe/Secur...ution-v2.0.pdf
Securing Optimizing Linux RH Edition (older): http://tldp.org/LDP/solrhe/Securing-...-Edition-v1.3/
Linux Security HOWTO: http://tldp.org/HOWTO/Security-HOWTO/index.html
Linux Security Quick Reference Guide (PDF): http://www.tldp.org/REF/ls_quickref/QuickRefCard.pdf
Security Quick-Start HOWTO for Linux,: http://tldp.org/HOWTO/Security-Quickstart-Redhat-HOWTO/
Security links at Linuxguru's: http://www.linuxguruz.org/z.php?id=914
TLPD Networking security HOWTO's: http://www.tldp.org/HOWTO/HOWTO-INDE...ml#NETSECURITY

Compromise, breach of security, detection
Intruder Detection Checklist (CERT): http://www.cert.org/tech_tips/intrud...checklist.html
Detecting and Removing Malicious Code (SF): http://www.securityfocus.com/infocus/1610
Steps for Recovering from a UNIX or NT System Compromise: http://www.cert.org/tech_tips/root_compromise.html
Formatting and Reinstalling after a Security Incident (SF): http://www.securityfocus.com/infocus/1692
How to Report Internet-Related Crime (usdoj.gov CCIPS): http://www.usdoj.gov/criminal/cybercrime/reporting.htm
Related, old(er) articles/docs:
Intruder Discovery/Tracking and Compromise Analysis: http://staff.washington.edu/dittrich...khat/blackhat/
Intrusion Detection Primer: http://www.linuxsecurity.com/feature...e_story-8.html
Through the Looking Glass: Finding Evidence of Your Cracker (LG): http://www.linuxgazette.com/issue36/kuethe.html
Recognizing and Recovering from Rootkit Attacks: http://www.cs.wright.edu/people/facu...on/obrien.html
See also post #5 under Forensics docs

Advisories, alerts, bulletins, disclosure, mailinglists, mailing archives, knowledge bases, other sites
Bugtraq (running): http://www.mail-archive.com/bugtraq@securityfocus.com/
or http://msgs.securepoint.com/cgi-bin/...q-current.html
or http://www.der-keiler.de/Mailing-Lis...focus/bugtraq/
or RSS: http://www.djeaux.com/rss/insecure-full-bugtraq.rss
Linuxsecurity: http://www.linuxsecurity.com
or RSS (Advisories): http://www.linuxsecurity.com/static-...advisories.rss
or RSS (News articles): http://www.linuxsecurity.com/static-...y_articles.rss
Securityfocus: http://www.securityfocus.com
or RSS (Vulns): http://www.securityfocus.com/rss/vulnerabilities.xml
Securiteam: http://www.securiteam.com/
CERT KB: http://www.cert.org/kb/
Securitytracker (Advisories): http://www.securitytracker.com/topics/topics.html
SANS RSS (ISC): http://iscxml.sans.org/rssfeed.xml

Neohapsis (mailinglists/archives): http://www.neohapsis.com
theaimsgroup (mailinglists/archives): http://marc.theaimsgroup.com/
Der Keiler (mailinglists/archives): http://www.der-keiler.de/

Linux Gazette: http://www.linuxgazette.com
Experts exchange: http://www.experts-exchange.com
The Linux Documentation Project: http://www.tldp.org
Blacksheep (HOWTO's, whitepapers, etc): http://www.blacksheepnetworks.com/security/
IRIA: http://www.ists.dartmouth.edu/IRIA/k...base/index.htm
E-secure-db Security Information database: http://www.e-secure-db.us/dscgi/ds.p...ollection-1586
Linuxmag, Hardening Linux Systems: http://www.linux-mag.com/2002-09/guru_01.html
SEI: http://www.sei.cmu.edu/publications/lists.html
Matt's Unix Security Page: http://www.deter.com/unix/
Jay Beale's docs (Bastille-linux/CIS): http://www.bastille-linux.org/jay/se...icles-jjb.html
The Unix Auditor's Practical Handbook: http://www.nii.co.in/tuaph.html
Aging stuff from Phrack like "Unix System Security Issues": www.fc.net/phrack/files/p18/p18-7.html

Mailinglists distro specific:
RedHat
http://www.redhat.com/support/errata/
http://www.redhat.com/mailing-lists/...ist/index.html

Debian
Our own markus1982 on a roll! LQ HOWTO: securing debian: http://www.linuxquestions.org/questi...threadid=61670
http://bugs.debian.org/
http://lists.debian.org/ (search for debian-security@lists.debian.org)
http://security.debian.org/

S.u.S.E.
mailto:suse-security@suse.com
mailto:suse-security-announce@suse.com
(subscribe: mailto:suse-security-subscribe@suse.com)

Mandriva
http://www.mandriva.com/en/security/advisories

Conectiva Linux
http://distro.conectiva.com/seguranca/
mailto:seguranca@distro.conectiva.com.br (subscribe for URL above URL; security-mailinglist Lingua Franca is Portugese, but on updates-mailinglist it's Engish. The last one always has the packages updates announced on security-mailinglist.

Slackware
http://www.slackware.com/lists/
mailto:slackware-security@slackware.com (subscribe for URL above)

# We need to incorporate more distro's here.

Hardening, distro specific
Debian/Mandrake/Red Hat: Bastille Linux: http://www.bastille-linux.org/
Debian Security HOWTO: http://www.debian.org/doc/manuals/se...-debian-howto/
Debian Security FAQ: http://www.debian.org/security/faq
Mandrake: msec-*.rpm: http://www.linux-mandrake.com/
SuSE: http://www.suse.de/~marc/
Slackware: Slackware Administrators Security tool kit: http://sourceforge.net/projects/sastk/
Slackware: http://members.cox.net/laitcg/new/system-hardening.txt

Log analysis tools, resources
Auditd: Linux Audit: http://people.redhat.com/sgrubb/audit/
Auditd: CAPP rules example: http://www.math.ias.edu/doc/audit-1.0.3/capp.rules
Tools & Tips for auditing code: http://www.vanheusden.com/Linux/audit.html
Track unlink syscall (rm): TrackFS, libauditunlink, LAUS, LTT (Syscalltrack on 2.4)
# FWanalog (Summarizes IPF & IPtables firewall logs)
# FWlogsum (Summarizes Checkpoint FW1 logs)
# FWlogwatch (Summarizes firewall & IDS logs)
# KLogger (WinNT/Win2K keystroke logger)
# Linux Event Logger (For Enterprise-Class Systems): http://evlog.sourceforge.net/
# Lmon (PERL-based real time log monitoring solution)
# LogSentry (Monitors logs for security violations)
# Logsurfer (Monitors logs in realtime)
# PIdentd (Provides UserID with TCP connects)
# Swatch (Monitors syslog messages)
# Secure Remote Syslogger (Encrypted streaming syslog)
# SnortSnarf (HTMLized Snort Log Reviewer)
# Syslog-NG (Replacement for standard syslog facility)
# Syslog.Org (Vast info on syslogging)
# Throughput Monitor (An event counter per timeframe log analyzer): http://home.uninet.ee/~ragnar/throughput_monitor/
Loganalysis.org (check the library): http://www.loganalysis.org/
Counterpane, Log Analysis Resources: http://www.counterpane.com/log-analysis.html
EVlog, Linux Event Logging for Enterprise-class systems
Throughput Monitor
Need to add: Snare, LTK etc etc

Daemons, device or application specific
The Linux-PAM System Administrators Guide
Securing Xwindows: http://www.uwsg.indiana.edu/usail/ex...d/xsecure.html
How to Build, Install, Secure & Optimize Xinetd: #(link gone, see: http://web.archive.org/web/200410121...netd/index.php)
Installation of a secure webserver (SuSE): #(link gone, do a websearch for "suse_secure_webserver.txt")
Linksys security (LQ notes on): http://www.linuxquestions.org/questi...007#post157007

Auditing tools at:
Packetstorm: http://www.packetstormsecurity.org/UNIX/audit/
SecurityFocus: http://www.securityfocus.com/tools/category/1

More Brainfood, sites, books
Daryl's TCP/IP primer: www.tcpipprimer.com
Teach Yourself TCP IP in 14 Days (PDF): http://www.bitman.ca/manuals.html click on the link to download a 1.3 Meg PDF
Uri's TCP resource list: www.private.org.il/tcpip_rl.html
Macmillan's "Maximum Security"
O'Reilly's TCP/IP Network Administration
* O'Reilly has a myriad of books some of which can also be found online, just search for "O'reilly and bookshelf", "o'reilly reference bookshelf" or "o'reilly cd bookshelf".

*Please note the easiest way to troubleshoot Netfilter related problems is to add log (target) rules before any "decision" in a chain.
** Please note there's a LOT of firewall scripts on LQ: just search the Linux - Security and Linux - networking fora please.

Netfilter/Iptables
LQ search, iptables+howto: http://www.linuxquestions.org/questi...der=descending
IPTables Tutorial: http://iptables-tutorial.frozentux.n...-tutorial.html
IPSysctl Tutorial: http://ipsysctl-tutorial.frozentux.n...-tutorial.html
Linuxguruz.org: http://www.linuxguruz.org/iptables/
Netfilter.org Packetfiltering HOWTO: http://www.netfilter.org/unreliable-...ltering-HOWTO/
Linuxsecurity.com Iptables tutorial: http://www.linuxsecurity.com/resourc...-tutorial.html
Iptables Connection tracking: http://www.cs.princeton.edu/~jns/sec...conntrack.html
Taking care of the New-not-SYN vulnerability: http://archives.neohapsis.com/archiv...3-01/0036.html

Ipchains
TLDP Ipchains HOWTO: http://www.linuxdoc.org/HOWTO/IPCHAINS-HOWTO.html
Flounder.net Ipchains HOWTO: http://www.flounder.net/ipchains/ipchains-howto.html

Web-browsers, mail clients, FTP clients, IM, P2P ports database for building your own rules: http://www.pcflank.com/fw_rules_db.htm

Other resources/misc stuff
Basic introduction to building ipchains rules: www.linuxdoc.org/HOWTO/IPCHAINS-HOWTO.html
Explanation of the Ipchains logformat: logi.cc/linux/ipchains-log-format.php3
Ipchains log decoder: dsl081-056-052.dsl-isp.net/dmn/decoder/decode.php
Basics on firewalling: www.linuxdoc.org/HOWTO/Firewall-HOWTO.html
linux-firewall-tools: http://www.linux-firewall-tools.com/linux/
CERT: Home Network Security: http://www.cert.org/tech_tips/home_networks.html
Firewall FAQ: http://www.faqs.org/faqs/firewalls-faq/
Assigned ports > 1024: http://www.ec11.dial.pipex.com/port-num4.shtml
Port designations: http://www.chebucto.ns.ca/~rakerman/port-table.html
Firewall Forensics FAQ (What am I seeing?): http://www.robertgraham.com/pubs/firewall-seen.html
Linux Firewall and Security Site: http://www.linux-firewall-tools.com/linux/
Auditing Your Firewall Setup (old, still usefull), : http://www.enteract.com/~lspitz/audit.html
TLDP: Firewall Piercing mini-HOWTO: http://www.tldp.org/HOWTO/mini/Firew...cing/x189.html
Something called the "Home PC Firewall Guide": http://www.firewallguide.com/
Vendor/Ethernet MAC Address Lookup: http://www.coffer.com/mac_find/
Netfilter Iptabes/Ipchains Log Format: http://logi.cc/linux/netfilter-log-format.php3
Dshield (find out if IP was marked as used in attacks): http://www1.dshield.org/ipinfo.php
Port search (Snort): http://www.snort.org/ports.html
Neohapsis Port search: http://www.neohapsis.com/neolabs/neo-ports/
P2P ports (IPMasq): http://www.tsmservices.com/masq/cfm/main.cfm
Is "Stealth" important?: http://www.practicallynetworked.com/...et.htm#Stealth
Infosyssec's Firewall Security and the Internet (badly updated site): http://www.infosyssec.net/infosyssec/firew1.htm

Webbased portscan services
http://www.linux-sec.net/Audit/nmap.test.gwif.html
http://www.derkeiler.com/Service/PortScan/
http://scan.sygatetech.com/
http://www.sdesign.com/securitytest/
http://www.auditmypc.com/
http://www.dslreports.com/scan
http://crypto.yashy.com/nmap.php
http://www.grc.com/

DoS info
Hardening the TCP/IP stack to SYN attacks: http://www.securityfocus.com/infocus/1729
SANS, Help Defeat Denial of Service Attacks: Step-by-Step: http://www.sans.org/dosstep/index.htm
SANS, ICMP Attacks Illustrated: http://rr.sans.org/threats/ICMP_attacks.php
CERT, Denial of Service Attacks: http://www.cert.org/tech_tips/denial_of_service.html
NWC, Fireproofing Against DoS Attacks (forms of): http://www.nwc.com/1225/1225f38.html

DDoS info
SANS, Consensus Roadmap for Defeating Distributed Denial of Service Attacks: http://www.sans.org/ddos_roadmap.htm
SANS, Spoofed IP Address Distributed Denial of Service Attacks: Defense-in-Depth: http://rr.sans.org/threats/spoofed.php
SANS, Understanding DDOS Attack, Tools and Free Anti-tools with Recommendation: http://rr.sans.org/threats/understan...nding_ddos.php
Juniper.net, Minimizing the Effects of DoS Attacks: http://arachne3.juniper.net/techcent...te/350001.html
CISCO, Strategies to Protect Against Distributed Denial of Service (DDoS) Attacks: http://www.cisco.com/warp/public/707/newsflash.html
Dave Dittrich's references: http://staff.washington.edu/dittrich/misc/ddos/
Xinetd Sensors: http://www.gate.net/~ddata/xinetd-sensors.html
Xinetd FAQ: http://synack.net/xinetd/faq.html

Note: vulnerability checking: CIS, SATAN, COPS, Tiger

FAQ: Network Intrusion Detection Systems: http://www.robertgraham.com/pubs/net...detection.html
Sniffin' the Ether v2.0: http://www.unixgeeks.org/security/ne...r/sniffer.html
Lotek sniffing docs: http://www.l0t3k.org/security/documents/sniffing/
Defeating Sniffers and Intrusion Detection Systems, Phrack, http://www.phrack.org/show.php?p=54&a=10

The IDS acronym game:

IDS: Intrusion Detection System refers to an application able to examine traffic for attributes and properties that mark "benign", suspicious, restricted, forbidden or outright hostile activities.

NIDS: Network IDS refers to Intrusion Detection, like running "sensors" on various sentry or sniffer hosts while logging and/or logprocessing and alerting is done on a central host (many-to-one topology).
NIDS examples are:
Snort: http://www.snort.org/
Shoki: http://shoki.sourceforge.net/
Prelude: http://www.prelude-ids.org/
OSSIM (Snort+Acid+mrtg+NTOP+OpenNMS+nmap+nessus+rrdtool): http://sourceforge.net/projects/os-sim/
MIDAS: http://midas-nms.sourceforge.net/
Firestorm: http://www.scaramanga.co.uk/firestorm/
Panoptis (DoS, DDoS only):
Defenseworx:
SHADOW:
Pakemon:
Some commercial/non OSS examples: Demarc PureSecure, Cisco Secure IDS (NetRanger), ISS Real Secure, Axent Net Prowler, Recourse ManHunt, NFR Network Flight Recorder, NAI CyberCop Network, Enterasys Dragon and Okena Stormfront/Stormwatch.
Snort also is available commercially these days.

HIDS: Host-based IDS. The HIDS acronym itself is subject to flamewars.
IDS examples are Snort, Shoki, Prelude, Defenseworx, Pakemon, Firestorm and Panoptis (DoS, DDoS only).

IPS: Intrusion Protection System. Passive or active (learning, like the heuristics stuff?) enforcement of rules at the application, system or access level. I suppose we're looking at stuff like Grsecurity, Solar Designer's Open Wall, LIDS, LOMAC, RSBAC, Linux trustees, Linux Extended Attributes, LIDS or Systrace here.
Commercial/non OSS examples: Entercept, ISS RealSecure, Axent Intruder Alert Manager, Enterasys' Dragon, Tripwire, Okena and CA's eTrust.

Docs:
Intrusion Detection Systems: An Introduction: http://www.linuxsecurity.com/feature...story-143.html
Intrusion Detection FAQ (SANS, handling ID in general): http://www.sans.org/resources/idfaq/index.php
Basic File Integrity Checking (with Aide): http://online.securityfocus.com/infocus/1408
www.networkintrusion.co.uk (IDS, NIDS, File Integrity Checkers)

Snort basics:
Using Snort as an IDS and Network Monitor in Linux (SANS, PDF file): http://www.giac.org/practical/gsec/James_Kipp_GSEC.pdf
Snort: IDS Installation with Mandrake 8.2, Snort, Webmin, Roxen Webserver, ACID, MySQL: http://www.linux-tip.net/workshop/id.../ids-snort.htm
ArachNIDS (Snort/Dragon/Defenseworx/Pakemon/Shoki rule, research and info library): http://whitehats.com/ids/
Intrusion Detection and Network Auditing on the Internet: http://www.infosyssec.net/infosyssec/intdet1.htm
Snort Stealth Sniffer: Paranoid Penguin: Stealthful Sniffing, Intrusion Detection and Logging: http://www.linuxjournal.com/article.php?sid=6222

Dropping Packets with Snort:
Why not to use Snort's "flexresp": http://www.mcabee.org/lists/snort-us.../msg00379.html
Snortsam: http://www.snortsam.net
Hogwash: http://hogwash.sourceforge.net
Snort-inline: http://www.snort.org/dl/contrib/patc...ort-inline.tgz
Guardian: see the Snort tarball, in the contrib dir.
Blockit:

Snort GUI's, management, log reporting and analysis:
Midas: http://midas-nms.sourceforge.net
SnortCenter: http://users.pandora.be/larc
Snort Unified Logging: Barnyard: (Sourceforge)
Snort Unified Logging: Logtopcap
Snort Unified Logging: Mudpit
Analysis Console for Intrusion Databases (ACID): http://acidlab.sourceforge.net/
HOWTO Build Snort with ACID: http://www.sfhn.net/whites/snortacid.htm
ACID HOWTO: http://www.andrew.cmu.edu/~rdanyliw/...snortacid.html
ACID FAQ: http://www.andrew.cmu.edu/~rdanyliw/snort/acid_faq.html
SPADE, Snortsnarf: http://www.silicondefense.com
Sguil: http://sguil.sourceforge.net/
Enabling Automated Detection of Security Events that affect Multiple Administrative Domains: http://www.incident.org/thesis/book1.html
Demarc (commercial): http://www.demarc.com
RazorBack: http://www.intersectalliance.com/pro...ack/index.html
Oinkmaster (rulemanagement): http://www.snort.org/dl/contrib/sign...nt/oinkmaster/
Snort alert mailer (C or .pe?r?l?): http://rouxdoo.freeshell.org/dmn/snort/
Pig Sentry: http://web.proetus.com/tools/pigsentry/
IDS Policy Manager Version (W32): http://www.activeworx.com/
Snort_stat: snort_stat.pl /var/log/snort/alert | /usr/lib/sendmail <human@someh.ost>
Swatch: ./swatch -c /root/.swatchrc --input-record-separator="\n\n" --read-pipe="tail -f /var/log/snort/alert" --daemon
Swatch + Hogtail.

Snort vs Abacus Portsentry:
Snort and PortSentry compared: http://www.linux.ie/articles/portsen...rtcompared.php

Comparison of IDSs ( NFR NID, Snort, INBOUNDS, SHADOW, Dragon, Tripwire): http://zen.ece.ohiou.edu/~nagendra/compids.html

Snort help, mailinglist (archives), honeypots:
Snort: Database support FAQ: http://www.incident.org/snortdb/
Snort mailinglists, Aims: http://marc.theaimsgroup.com/
Snort IDS forum at Whitehats.com: http://whitehats.com/cgi/forum/messa...?bbs=forum&f=4
Baby steps with a honeypot: http://www.lucidic.net/whitepapers/mcooper-4-2002.html
Honeypot & Intrusion Detection Resources: http://www.honeypots.net/
The TCP Flags Playground (Mailinglist, Neohapsis): http://archives.neohapsis.com/archiv...0-03/0386.html

Snort + 802.11 aka Wireless: http://www.loud-fat-bloke.co.uk/w80211.html

Sniffing (network wiretap, sniffer) FAQ: http://www.robertgraham.com/pubs/sniffing-faq.html
Apps, network monitoring (index): http://www.mirrors.wiretapped.net/se...ng-README.txt.

An Analysis of a Compromised Honeypot (Snort+Ethereal): http://www.securityfocus.com/infocus/1676
To add: Firestorm NIDS, Barnyard, Mudpit, Snort GUI's, add-ons etc etc.

Snort on two interfaces, solution one: "-i bond0".
Valid-for: running one Snort instance, multiple promiscuous mode interfaces except the mgmnt one.
Caveat: none
See-also: Documentation/networking/bonding.txt
Do once: "echo alias bond0 bonding >>/etc/modules.conf"
At boot: "ifconfig bond0 up; ifenslave bond0 eth0; ifenslave bond0 eth1"
At boot: start Snort with interface arg "-i bond0"

Snort on two interfaces, solution two: "-i any"
Valid-for: running one Snort instance, all interfaces.
Caveat: you loose promiscuous mode.
See-also:
At boot: start Snort with interface arg "-i any" and a BPF filter to stop it from logging the loopback device.

File Integrity Detection Systems
Checking a filesystem's contents against one or more checksums to determine if a file (remember anything essentially is a file on a Linux FS) has been changed.
Examples are:
Aide: http://www.cs.tut.fi/~rammer/aide.html (for remote mgmnt see also ICU http://www.algonet.se/~nitzer/ICU/ or RFC http://sourceforge.net/projects/rfc/ which handles Aide, Integrit and Afick)
Samhain: http://la-samhna.de/samhain/ (for remote mgmnt see docs)
Osiris: http://osiris.shmoo.com/
Nabou: http://www.daemon.de/en/software/nabou/
Sentinel: http://zurk.sourceforge.net/zfile.html
Viper(DB): http://panorama.sth.ac.at/viperdb/
Integrit: http://integrit.sourceforge.net/
Tripwire (for remote mgmnt see FICC: http://freshmeat.net/projects/ficc/).
Chkrootkit (not only Linux): http://www.chkrootkit.org
Rootkit Hunter (not only Linux): http://rkhunter.sourceforge.net
Findkit: http://mirror.trouble-free.net/killall/findkit

Commercial/non OSS examples: Versioner, GFI LANguard System Integrity Monitor, Ionx's Data Sentinel, Tripwire for Servers and Pedestal Software Intact.
File Integrity (SecurityFocus, tools list): http://www.securityfocus.com/tools/category/7

Viruses on Linux/GNU, Antivirus software

Sendmail, Tcpdump, OpenSSH, TCP Wrappers, Aide and some other projects have suffered from people succeeding to inject malicious code, and of those only Sendmail and OpenSSH where at main servers, the rest where mirrors AFAIK. Even though all the apps mentioned are safe to use, and the differences where noted soon, the real problem is you I. have to have the knowledge to read code, and II. the discipline to read the code each time and question any diffs or III. have minimal "protection" in place to cope with like rogue compiled apps "phoning home". Which in essence means to end users any SW provided w/o means to verify integrity of the code and the package should be treated with care, instead of accepting it w/o questioning.

As for the "virus" thingie I wish we, as a Linux community, try to "convert" people away from the typical troubles of Pitiful Operating Systems (abbrev.: POS, aka the MICROS~1 Game Platform) and direct them towards what's important to know wrt Linux: user/filesystem permissions, b0rken/suid/sgid software, worms, trojans and rootkits.

Basic measures should be:
- Using (demanding) source verification tru GPG or minimally md5sums,
- Watch system integrity (Aide, Samhain, Tripwire or any package mgr that can do verification: save those databases off-site, also see Tiger, Chkrootkit),
- Harden your systems by not installing SW you don't need *now*, denying access where not needed and using tools like Bastille-linux, tips from Astaro,
- Patch kernel to protect looking at/writing to crucial /proc and /dev entries and/or use ACL's (see Silvio Cesare's site, Grsecurity, LIDS),
- Watch general/distro security bulletins and don't delay taking action (Slapper, Li0n etc),
- Keep an eye on outgoing traffic (egress logging and filtering),
- Don't compile apps as root but as a non-privileged user,
- Inspect the code if you can,
- Don't use Linux warez,
But most of all: use common sense.

*If you're still not satisfied you've covered it all you could arm yourself with knowledge on forensics stuff like UML, chrooting, disassembly and honeypots.

If you want to find Antivirus software, Google the net for Central Command, Sophos, Mcafee, Kaspersky, H+BEDV, Trend Micro, Frisk, RAV, Clam, Amavis, Spam Assassin, Renattach, Ripmime, Milter or Inflex.
- AV SW is as good as it's signatures/heuristics. Some vendors don't update their Linux sig db's very well, or field SW with lacking capabilities. I've tested some (admittedly a long time ago) on my virus/trojan/LRK/malware libs. Bad (IMHO): Frisk's F-Prot (sigs), Clam (sigs), H+BEDV (libc version). Good (IMNSHO): Mcafee's uvscan (best) and RAV (2nd). Please do test yourself.
- AFAIK only KAV (Kaspersky) has a realtime scanner daemon. I'm in limbo about it's compatibility with recent kernels tho.

Links to check out:
LAVP/Mini-FAQ Linux/Unix AV SW,
NIST (list of AV vendors),
Clam.

Chroot Jails Made Easy with the Jail Chroot Project: http://www.linuxorbit.com/modules.ph...page&artid=538
Chrooting MySQL HOWTO (LQ): http://www.linuxquestions.org/questi...threadid=34338
and http://www.linuxquestions.org/questi...661#post206661
Apache, PHP, MySQL: http://www.faqts.com/knowledge_base/...aid/290/fid/31
SendMail: http://www.sendmail.net/000705securitygeneral.shtml
SendMail: http://www.linuxjournal.com/article.php?sid=5753
Snort: http://www.norz.org/software/snortstart.html

OpenSSH for chrooted sessions on Linux: http://mail.incredimail.com/howto/openssh/
http://chrootssh.sourceforge.net
OpenSSH, Scponly: http://www.sublimation.org/scponly/
Using scponly for secure file transfers: http://www.sancho2k.net/filemgmt_dat...s/scponly.html
OpenSSH, Rssh: http://pizzashack.org/rssh/
OpenSSH Sftp logging patch, contact Mike Martinez: mmartinez@reeusda.gov

How to chroot an Apache tree with Linux and Solaris: http://penguin.epfl.ch/chroot.html
An Overview of 'chroot jailing' Services in Linux: http://www.incidents.org/protect/borland.php
How to break out of a chroot() jail: http://www.bpfh.net/simes/computing/chroot-break.html
Breaking out of a restricted shell: http://online.securityfocus.com/infocus/1575, down at "Breaking Out of Various Restrictions"
Tech-Babble: Virtual Server Myth: http://www.pair.com/pair/current/ins...ualserver.html
0x05: Why chroot(2) Sucks: http://packetstormsecurity.nl/mag/napalm/napalm-12.txt
Chuvakin A.,: http://www.linuxsecurity.com/feature..._story-99.html
Chrooting daemons and system processes HOW-TO: http://www.networkdweebs.com/chroot.html

Other SW/HOWTO's unsorted
http://www.gsyc.inf.uc3m.es/~assman/jail
http://www.opensourcedirectory.org/projects/jailchootp/
http://people.debian.org/~pzn/howto/chroot-bind.sh.txt
http://www.linuxdocs.org/HOWTOs/Chroot-BIND-HOWTO.html
http://www.linuxdoc.org/HOWTO/Chroot-BIND8-HOWTO.html
http://www.linuxsecurity.com/docs/HO...D-HOWTO-4.html
http://www.enteract.com/~robt/Docs/A...l-freebsd.html for BIND
http://hoohoo.ncsa.uiuc.edu/docs/tut...t-example.html
http://penguin.epfl.ch/chroot.html
http://tjw.org/chroot-login-HOWTO/
http://www.ssh.com/products/ssh/admi...hrootmgr_.html
http://rr.sans.org/linux/daemons.php
http://www.defcon1.org/html/Security...t-enforce.html
http://www.gnumonks.org/ftp/pub/netf...oot-howto.html
http://www.sunbeam.franken.de/projec...oot-howto.html
http://www.mlug.ca/sklav/stories/November_issue2001
http://www.floc.net/makejail/
http://www.balabit.hu/downloads/jailer

Forensics HOWTO's, docs
Steps for Recovering from a UNIX or NT System Compromise: http://www.cert.org/tech_tips/root_compromise.html
Open Web Application Security Project (OWASP): http://www.owasp.org/
Open Source Computer Forensics Manual: http://sourceforge.net/project/showf...ease_id=171701
OSSTM: Institute for Security and Open Methodologies (formerly ideahamster.org): http://www.isecom.org/projects/osstmm.htm
Forensics Basic Steps: http://staff.washington.edu/dittrich/misc/forensics/ or http://staff.washington.edu/dittrich...forensics.html
Dd and netcat cloning disks: http://www.rajeevnet.com/hacks_hints...s_cloning.html
Security Applications of Bootable Linux CD-ROMs: http://rr.sans.org/linux/sec_apps.php
Honeypot project (Hone your skills with the SOM): http://project.honeynet.org/scans/
RH8.0: Chapter 11. Incident Response (Red Hat Linux Security Guide): http://www.redhat.com/docs/manuals/l...se-invest.html
Forensics and Incident Response Resources: http://is-it-true.org/pt/ptips8.shtml
Forensics presentation by Weld Pond and Tan: http://www.cs.neu.edu/groups/acm/lectures/Forensics_NU/
Law Enforcement and Forensics Links.: http://www.computerforensics.net/links.htm
Forensics commercial svc's: http://forensic.to/links/pages/Foren...Investigation/

Forensics CDR's
FIRE (formerly Biatchux +TCT): http://biatchux.dmzs.com/?section=main
The Penguin Sleuth Kit (Knoppix-based +TCT + Sleuthkit): http://luge.cc.emory.edu/psl.html
Knoppix

Forensics tools
OSSTM Tools listing: http://www.isecom.org/projects/operationaltools.htm
The Coroners Toolkit (TCT): http://www.porcupine.org/forensics/ or http://www.fish.com/forensics/
tomsrtbt (1 floppy distro): http://www.toms.net/rb/
Trinux, (Pentest/sniff/scan/recovery/IDS/forensics CD): http://www.trinux.org/
Snarl (Forensics CD based on FreeBSD): http://snarl.eecue.com
Freeware Forensics Tools for Unix: http://online.securityfocus.com/infocus/1503
The @stake Sleuth Kit (TASK): http://sleuthkit.sourceforge.net/
Tools used by CSIRTs to Collect Incident Data/Evidence, Investigate and Track Incidents (list): http://www.uazone.org/demch/analysis/sec-inchtools.html
Freeware Forensics Tools (reflist, Linux w32).: http://www.theiia.org/itaudit/index....=forum&fid=325
TUCOFS - The Ultimate Collection of Forensic Software, : http://www.tucofs.com/tucofs/tucofs.asp?mode=mainmenu
Response kits (precompiled static binaries for Linux, Slowaris and wintendo): http://www.incident-response.org/irtoolkits.htm
Precompiled static binaries for Linux (iso): http://www.stearns.org/staticiso/
Forensic Acquisition Utilities for w32: http://users.erols.com/gmgarner/forensics/
CREED (Cisco Router Evidence Extraction Disk),: http://cybercrime.kennesaw.edu/creed/
...else check Zone-h.org, Packetstorm, Wiretapped.net, whatever.

Undelete HOWTO's
Recovering a Lost Partition Table: http://tsaling.home.attbi.com/linux/lost_partition.html
Linux Partition HOWTO: http://surfer.nmr.mgh.harvard.edu/pa...Partition.html
How to recover lost partitions: http://cvs.sslug.dk/hdmaint/hdm_rescue.html
Linux Ext2fs Undeletion mini-HOWTO: http://www.linuxdoc.org/HOWTO/mini/E...ndeletion.html
Linux Partition Rescue mini-HOWTO: http://www.linux-france.org/article/...ini-HOWTO.html
File Recovery.v.0.81 (using Midnight Commander): http://www.ists.dartmouth.edu/text/I...very.v0.81.php

Rescue tools for partition table/ext2fs
Gpart: http://www.stud.uni-hannover.de/user/76201/gpart/
Testdisk: http://www.cgsecurity.org/index.html
Parted: http://www.gnu.org/software/parted/parted.html
Recover (app + info): http://recover.sourceforge.net/linux/recover/
R-Linux: http://www.r-tt.com/RLinux.shtml
Unrm: http://www.securiteam.com/tools/Unrm...for_Linux.html
Dd-rescue: http://www.garloff.de/kurt/linux/ddrescue/
Also see mc (the Midnight Commander)
TCT (above).

Rescue tools from dd image
Foremost: http://sourceforge.net/projects/foremost/

Rescue tools for FAT/VFAT/FAT32 from Linux
Fatback: http://sourceforge.net/projects/biatchux/

Partition imaging
: http://www.partimage.orgPartimage.
* For more rescue tools check Freshmeat.net, metalab.unc.edu or other depots for a /Linux/system/recovery/ dir.

II. Runefs: The first inode that can allocate block resources on a ext2 file system is in fact the bad blocks inode (inode 1) -- *not* the root inode (inode 2). Because of this mis-implementation of the ext2fs it is possible to store data on blocks allocated to the bad blocks inode and have it hidden from an analyst using TCT or TASK. To illustrate the severity of this attack the following examples demonstrate using the accompanying runefs toolkit to: create hidden storage space; copy data to and from this area, and show how this area remains secure from a forensic analyst.: http://www.phrack.org/show.php?p=59&a=6

//If you've read this far and you aren't a professional system administrator: congrats. LQ doesn't ask you nothing in return but to spread around whatever good security practices you know. If you want to add a section or a link: please email me. License information: see top of thread.