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Linux Security

Linux Security. Keeping Your System Safe. What Are the Threats?. Local Threats. Curious employees. Disgruntled employees Errant programs/applications. Unauthorized personnel. Remote Threats. Unauthorized Dial-in access. Unauthorized Internet Access Script Kiddies

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Linux Security

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  1. Linux Security Keeping Your System Safe

  2. What Are the Threats?

  3. Local Threats • Curious employees. • Disgruntled employees • Errant programs/applications. • Unauthorized personnel.

  4. Remote Threats • Unauthorized Dial-in access. • Unauthorized Internet Access • Script Kiddies • Viruses, Worms, Trojan Horses, etc.

  5. Thank You, Microsoft • All Microsoft Operating Systems are insecure by design. • Ease of use features typically are security threats, i.e. ability to automatically run scripts and programs delivered through email. • Majority of threats aimed at Microsoft Operating Systems. • Outlook scripts • IIS weaknesses • Microsoft services weaknesses, i.e., DNS, Bind, etc. • Good because it keeps them away from Linux/Unix; bad because it encourages them to try.

  6. How Real Are the Threats? • Recent media coverage is one indication • Corporate firewall logs show constant increases. • Sites such as http://www.dshield.org tracking security threats show increased attempts. • All systems, including personal systems are at risk.

  7. A Simple Home Installation • November 2000, I installed a cable modem and firewall: • Why? Compaq requires hardware firewalls and I felt more comfortable with one. • Home network consists of 3 computers on line full time and notebook when working from home. • Service is with Cablevision through cable modem. • No servers anywhere in my network • Firewall has ping reply turned off • No machine internal to firewall is visible outside the network. • Security tested courtesy of ShieldsUp at http://grc.com

  8. My Firewall Log WAN Type: Dynamic IP Address (R1.93e) Display time: Monday, July 30, 2001 20:46:15 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:41 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Friday, July 27, 2001 21:57:42 Unrecognized access from 64.224.17.142:21548 to UDP port 6970 Saturday, July 28, 2001 02:55:12 Unrecognized access from 24.26.235.214:1819 to TCP port 27374 Saturday, July 28, 2001 02:55:15 Unrecognized access from 24.26.235.214:1819 to TCP port 27374 Saturday, July 28, 2001 02:55:21 Unrecognized access from 24.26.235.214:1819 to TCP port 27374 Saturday, July 28, 2001 02:55:33 Unrecognized access from 24.26.235.214:1819 to TCP port 27374 Saturday, July 28, 2001 05:19:07 Unrecognized access from 24.191.124.172:2525 to TCP port 27374 Saturday, July 28, 2001 05:19:10 Unrecognized access from 24.191.124.172:2525 to TCP port 27374 Saturday, July 28, 2001 05:19:16 Unrecognized access from 24.191.124.172:2525 to TCP port 27374 Saturday, July 28, 2001 05:19:27 Unrecognized access from 24.191.124.172:2525 to TCP port 27374 Saturday, July 28, 2001 05:38:58 DHCP:renew Saturday, July 28, 2001 05:38:58 DHCP:ack(DOL=302400,T1=151200,T2=264600)

  9. Saturday, July 28, 2001 06:35:07 Unrecognized access from 24.28.123.241:3722 to TCP port 1243 Saturday, July 28, 2001 06:35:07 Unrecognized access from 24.28.123.241:3723 to TCP port 27374 Saturday, July 28, 2001 06:35:10 Unrecognized access from 24.28.123.241:3723 to TCP port 27374 Saturday, July 28, 2001 06:35:10 Unrecognized access from 24.28.123.241:3722 to TCP port 1243 Saturday, July 28, 2001 06:35:16 Unrecognized access from 24.28.123.241:3723 to TCP port 27374 Saturday, July 28, 2001 06:35:16 Unrecognized access from 24.28.123.241:3722 to TCP port 1243 Saturday, July 28, 2001 06:35:28 Unrecognized access from 24.28.123.241:3723 to TCP port 27374 Saturday, July 28, 2001 06:35:28 Unrecognized access from 24.28.123.241:3722 to TCP port 1243 Saturday, July 28, 2001 08:36:09 Unrecognized access from 216.128.206.5:4974 to TCP port 111 Saturday, July 28, 2001 09:03:17 Unrecognized access from 24.191.49.172:2996 to TCP port 27374 Saturday, July 28, 2001 09:03:20 Unrecognized access from 24.191.49.172:2996 to TCP port 27374 Saturday, July 28, 2001 09:03:26 Unrecognized access from 24.191.49.172:2996 to TCP port 27374 Saturday, July 28, 2001 09:03:38 Unrecognized access from 24.191.49.172:2996 to TCP port 27374 Saturday, July 28, 2001 10:15:47 Unrecognized access from 24.188.129.85:137 to UDP port 137 Saturday, July 28, 2001 10:15:49 Unrecognized access from 24.188.129.85:137 to UDP port 137 Saturday, July 28, 2001 10:15:50 Unrecognized access from 24.188.129.85:137 to UDP port 137 Saturday, July 28, 2001 15:39:41 Unrecognized access from 210.96.22.193:4603 to TCP port 515 Saturday, July 28, 2001 16:31:50 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:31:51 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:31:53 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:31:54 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:31:56 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:31:57 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:08 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:09 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:11 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:12 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:14 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 16:32:15 Unrecognized access from 24.132.249.27:137 to UDP port 137 Saturday, July 28, 2001 17:24:45 Unrecognized access from 24.1.138.43:3398 to TCP port 27374 Saturday, July 28, 2001 17:24:48 Unrecognized access from 24.1.138.43:3398 to TCP port 27374 Saturday, July 28, 2001 17:24:54 Unrecognized access from 24.1.138.43:3398 to TCP port 27374 Saturday, July 28, 2001 17:25:06 Unrecognized access from 24.1.138.43:3398 to TCP port 27374 Saturday, July 28, 2001 19:57:21 Unrecognized access from 209.136.35.2:111 to TCP port 111 Saturday, July 28, 2001 22:31:44 sagan sent a job to printer Saturday, July 28, 2001 22:32:39 job was done Saturday, July 28, 2001 22:53:06 sagan sent a job to printer Saturday, July 28, 2001 22:53:53 job was done Sunday, July 29, 2001 07:41:29 roddenberry sent a job to printer Sunday, July 29, 2001 07:53:39 job was done Sunday, July 29, 2001 07:53:47 roddenberry sent a job to printer Sunday, July 29, 2001 08:02:57 job was done Sunday, July 29, 2001 08:03:07 roddenberry sent a job to printer Sunday, July 29, 2001 08:07:19 job was done Sunday, July 29, 2001 09:18:44 roddenberry sent a job to printer Sunday, July 29, 2001 09:19:37 job was done

  10. Sunday, July 29, 2001 12:20:07 Unrecognized access from 24.21.173.44:1198 to TCP port 27374 Sunday, July 29, 2001 12:20:10 Unrecognized access from 24.21.173.44:1198 to TCP port 27374 Sunday, July 29, 2001 12:20:16 Unrecognized access from 24.21.173.44:1198 to TCP port 27374 Sunday, July 29, 2001 12:20:28 Unrecognized access from 24.21.173.44:1198 to TCP port 27374 Sunday, July 29, 2001 13:18:58 Unrecognized access from 24.43.164.99:3729 to TCP port 27374 Sunday, July 29, 2001 13:19:01 Unrecognized access from 24.43.164.99:3729 to TCP port 27374 Sunday, July 29, 2001 13:19:07 Unrecognized access from 24.43.164.99:3729 to TCP port 27374 Sunday, July 29, 2001 13:19:19 Unrecognized access from 24.43.164.99:3729 to TCP port 27374 Sunday, July 29, 2001 15:31:25 Unrecognized access from 216.12.192.2:2070 to TCP port 27374 Sunday, July 29, 2001 15:31:28 Unrecognized access from 216.12.192.2:2070 to TCP port 27374 Sunday, July 29, 2001 15:31:28 Unrecognized access from 216.12.192.2:2069 to TCP port 1243 Sunday, July 29, 2001 15:31:34 Unrecognized access from 216.12.192.2:2070 to TCP port 27374 Sunday, July 29, 2001 15:31:34 Unrecognized access from 216.12.192.2:2069 to TCP port 1243 Sunday, July 29, 2001 15:31:47 Unrecognized access from 216.12.192.2:2070 to TCP port 27374 Sunday, July 29, 2001 15:31:47 Unrecognized access from 216.12.192.2:2069 to TCP port 1243 Sunday, July 29, 2001 18:58:02 Unrecognized access from 211.254.60.205:2892 to TCP port 111 Sunday, July 29, 2001 18:58:16 Unrecognized access from 211.254.60.205:2892 to TCP port 111 Sunday, July 29, 2001 19:13:01 Unrecognized access from 24.167.33.147:137 to UDP port 137 Sunday, July 29, 2001 19:13:03 Unrecognized access from 24.167.33.147:137 to UDP port 137 Sunday, July 29, 2001 19:13:04 Unrecognized access from 24.167.33.147:137 to UDP port 137 Sunday, July 29, 2001 19:14:05 Unrecognized access from 211.96.5.74:3308 to TCP port 111 Sunday, July 29, 2001 19:14:44 Unrecognized access from 217.58.40.251:3349 to TCP port 515 Sunday, July 29, 2001 19:14:47 Unrecognized access from 217.58.40.251:3349 to TCP port 515 Sunday, July 29, 2001 20:43:48 Unrecognized access from 24.186.80.220:137 to UDP port 137 Sunday, July 29, 2001 20:43:49 Unrecognized access from 24.186.80.220:137 to UDP port 137 Sunday, July 29, 2001 20:43:51 Unrecognized access from 24.186.80.220:137 to UDP port 137 Sunday, July 29, 2001 22:21:38 Unrecognized access from 128.121.244.93:2402 to TCP port 27374 Sunday, July 29, 2001 22:56:28 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 22:56:29 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 22:56:31 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 22:56:32 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 22:56:34 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 22:56:35 Unrecognized access from 66.26.119.191:137 to UDP port 137 Sunday, July 29, 2001 23:20:29 roddenberry sent a job to printer Sunday, July 29, 2001 23:21:42 job was done Sunday, July 29, 2001 23:39:00 DHCP:renew Sunday, July 29, 2001 23:39:00 DHCP:ack(DOL=302400,T1=151200,T2=264600) Monday, July 30, 2001 00:15:32 sagan sent a job to printer Monday, July 30, 2001 00:16:09 job was done Monday, July 30, 2001 02:57:00 Unrecognized access from 24.42.158.61:1702 to TCP port 111 Monday, July 30, 2001 02:57:03 Unrecognized access from 24.42.158.61:1702 to TCP port 111 Monday, July 30, 2001 05:57:27 Unrecognized access from 24.23.45.224:1598 to TCP port 27374 Monday, July 30, 2001 05:57:30 Unrecognized access from 24.23.45.224:1598 to TCP port 27374 Monday, July 30, 2001 06:52:44 Unrecognized access from 206.71.117.31:4223 to TCP port 27374 Monday, July 30, 2001 06:52:47 Unrecognized access from 206.71.117.31:4223 to TCP port 27374 Monday, July 30, 2001 11:11:13 Unrecognized access from 194.236.30.231:3691 to TCP port 1243 Monday, July 30, 2001 11:11:13 Unrecognized access from 194.236.30.231:3692 to TCP port 27374 Monday, July 30, 2001 11:11:16 Unrecognized access from 194.236.30.231:3692 to TCP port 27374

  11. Monday, July 30, 2001 11:11:16 Unrecognized access from 194.236.30.231:3691 to TCP port 1243 Monday, July 30, 2001 11:11:22 Unrecognized access from 194.236.30.231:3692 to TCP port 27374 Monday, July 30, 2001 11:11:22 Unrecognized access from 194.236.30.231:3691 to TCP port 1243 Monday, July 30, 2001 11:11:34 Unrecognized access from 194.236.30.231:3692 to TCP port 27374 Monday, July 30, 2001 11:11:34 Unrecognized access from 194.236.30.231:3691 to TCP port 1243 Monday, July 30, 2001 11:58:51 sagan sent a job to printer Monday, July 30, 2001 11:59:28 job was done Monday, July 30, 2001 12:02:18 sagan sent a job to printer Monday, July 30, 2001 12:02:56 job was done Monday, July 30, 2001 12:03:07 sagan sent a job to printer Monday, July 30, 2001 12:03:39 job was done Monday, July 30, 2001 12:03:47 sagan sent a job to printer Monday, July 30, 2001 12:04:22 job was done Monday, July 30, 2001 12:05:03 sagan sent a job to printer Monday, July 30, 2001 12:05:37 job was done Monday, July 30, 2001 12:06:06 sagan sent a job to printer Monday, July 30, 2001 12:06:41 job was done Monday, July 30, 2001 12:06:56 sagan sent a job to printer Monday, July 30, 2001 12:07:28 job was done Monday, July 30, 2001 12:07:33 sagan sent a job to printer Monday, July 30, 2001 12:08:11 job was done Monday, July 30, 2001 12:09:13 sagan sent a job to printer Monday, July 30, 2001 12:09:47 job was done Monday, July 30, 2001 12:09:59 sagan sent a job to printer Monday, July 30, 2001 12:10:30 job was done Monday, July 30, 2001 12:10:38 sagan sent a job to printer Monday, July 30, 2001 12:11:12 job was done Monday, July 30, 2001 12:11:31 sagan sent a job to printer Monday, July 30, 2001 12:12:05 job was done Monday, July 30, 2001 12:12:32 sagan sent a job to printer Monday, July 30, 2001 12:13:05 job was done Monday, July 30, 2001 12:13:34 sagan sent a job to printer Monday, July 30, 2001 12:14:08 job was done Monday, July 30, 2001 12:14:15 sagan sent a job to printer Monday, July 30, 2001 12:14:49 job was done

  12. Monday, July 30, 2001 12:18:13 Unrecognized access from 24.21.107.120:4310 to TCP port 27374 Monday, July 30, 2001 12:18:16 Unrecognized access from 24.21.107.120:4310 to TCP port 27374 Monday, July 30, 2001 12:18:22 Unrecognized access from 24.21.107.120:4310 to TCP port 27374 Monday, July 30, 2001 12:18:34 Unrecognized access from 24.21.107.120:4310 to TCP port 27374 Monday, July 30, 2001 13:35:18 Unrecognized access from 24.181.58.50:3538 to TCP port 27374 Monday, July 30, 2001 13:35:21 Unrecognized access from 24.181.58.50:3538 to TCP port 27374 Monday, July 30, 2001 13:35:27 Unrecognized access from 24.181.58.50:3538 to TCP port 27374 Monday, July 30, 2001 13:45:21 Unrecognized access from 65.30.161.170:137 to UDP port 137 Monday, July 30, 2001 13:45:22 Unrecognized access from 65.30.161.170:137 to UDP port 137 Monday, July 30, 2001 13:45:24 Unrecognized access from 65.30.161.170:137 to UDP port 137 Monday, July 30, 2001 14:37:16 Unrecognized access from 206.71.117.31:3956 to TCP port 27374 Monday, July 30, 2001 14:37:19 Unrecognized access from 206.71.117.31:3956 to TCP port 27374 Monday, July 30, 2001 14:37:45 Unrecognized access from 206.71.117.31:3333 to TCP port 27374 Monday, July 30, 2001 14:37:48 Unrecognized access from 206.71.117.31:3333 to TCP port 27374 Monday, July 30, 2001 15:04:29 Unrecognized access from 206.71.117.31:3615 to TCP port 27374 Monday, July 30, 2001 19:06:43 Unrecognized access from 24.157.38.120:137 to UDP port 137 Monday, July 30, 2001 19:06:43 Unrecognized access from 192.168.0.2:137 to UDP port 137 Monday, July 30, 2001 19:06:44 Unrecognized access from 192.168.0.2:137 to UDP port 137 Monday, July 30, 2001 19:06:44 Unrecognized access from 24.157.38.120:137 to UDP port 137 Monday, July 30, 2001 19:06:46 Unrecognized access from 24.157.38.120:137 to UDP port 137 Monday, July 30, 2001 19:06:46 Unrecognized access from 192.168.0.2:137 to UDP port 137 Monday, July 30, 2001 19:42:01 sagan sent a job to printer Monday, July 30, 2001 19:42:49 job was done Monday, July 30, 2001 20:04:49 Unrecognized access from 205.134.172.2:2549 to UDP port 53 Monday, July 30, 2001 20:15:38 Unrecognized access from 210.114.174.39:3717 to TCP port 515 Monday, July 30, 2001 20:15:41 Unrecognized access from 210.114.174.39:3717 to TCP port 515 Monday, July 30, 2001 20:46:07 192.168.123.120 login successful

  13. How Many Attackers? http://www.whois.net/ 64.224.17.142 INTERLAND.NET 24.26.235.214 RR.COM 24.191.124.172 Cablevision Systems Corp 24.28.123.241 RR.COM 216.128.206.5 Optilink Communications, Inc. 24.191.49.172 Cablevision Systems Corp 24.188.129.85 Cablevision Systems Corp 210.96.22.193 Asia Pacific Network Information Center* 24.132.249.27 European Regional Internet Registry 24.1.138.43 @Home Network 209.136.35.2 Huntleigh Telecommunications Group 24.21.173.44 @Home Network 24.43.164.99 Rogers@Home Wlfdle 216.12.192.2 Everyones Internet, Inc. 211.254.60.205 Asia Pacific Network Information Center* 24.167.33.147 ServiceCo LLC - Road Runner 211.96.5.74 Asia Pacific Network Information Center* 217.58.40.251 European Regional Internet Registry 24.186.80.220 Cablevision Systems Corp 128.121.244.93 Verio, Inc. 66.26.119.191 ROADRUNNER-MIDSOUTH 24.42.158.61 Rogers@Home 206.71.117.31 Microsoft 194.236.30.231 European Regional Internet Registry 24.21.107.120 @Home Network 24.181.58.50 @Home Network 65.30.161.170 ROADRUNNER-CENTRAL 206.71.117.31 Microsoft 24.157.38.120 *** Not listed *** 192.168.0.2 Reserved+ 24.157.38.120 Rogers@Home 205.134.172.2 Patuxent Publishing 210.114.174.39 Asia Pacific Network Information Center* * "Please do not send spam complaints to APNIC." + Reserved for LAN

  14. Popular Ports Scanned • 21 FTP • 23 Telnet • 25 SMTP • 79 Finger • 80 HTTP • 110 POP3 • 113 IDENT • 139 Net BIOS • 143 IMAP • 443 HTTPS

  15. If Linux Is Secure, Why Are You Here? • To expand on earlier statement, Linux is more secure than typical MS OS due to: • File systems with ownerships and access control lists • Multiuser design enforces password protection to system • Design based on Unix, which is more mature and has already faced many of these challenges • There are still security risks, many due to naïve system administration and bugs.

  16. The Road To A More Secure Linux • We’ll discuss general security risks, so that we can gain a background in security. • We’ll look at securing the system locally, then over the network. • We’ll present resources to help us identify threats.

  17. Security Primer

  18. Common Vulnerabilities • Default installs of operating systems and applications • Accounts with No Passwords or Weak Passwords • Non-existent or Incomplete Backups • Large number of open ports • Not filtering packets for correct incoming and outgoing addresses • Non-existent or incomplete logging • Vulnerable CGI Programs

  19. UNIX Vulnerabilities • Buffer Overflows in RPC Services • Sendmail Vulnerabilities • Bind Weaknesses • R* Commands (rlogin, rsh and rexec) • LPD (remote print protocol daemon) • sadmind and mountd • Default SNMP Strings

  20. What Should I Do?

  21. Establish a Security Policy • Adopt the policy: “That which is not permitted is prohibited.” • rfc1244 describes how to create your own network security policy. • rfc1281 is an example security policy with detailed descriptions of each step. • Look at example policies such as the COAST policy archive at ftp://coast.cs.purdue.edu/pub/doc/policy to

  22. Linux General Security

  23. Physical Security • Physically secure the computer • Physically place computers in secure areas. • Use front panel locks to prevent tampering.

  24. System Boot Security • Don’t allow someone access by simply rebooting the system • Set bios boot password. • Set bios administration password. • Set boot loader, I.e., lilo, passwords

  25. Login Security • Make certain all accounts have strong passwords. • Make sure all users never leave open terminals and consoles • vlock • xlock

  26. User Security • Never give out root priviledges. • Don’t use rsh, rlogin, rexec as root • Never use telnet or ftp as root. • Minimize access points by root by modifying /etc/securetty.

  27. File System Security • Set default umask to be as restrictive as possible. • Export file systems over NFS as read only unless absolutely necessary. • Avoid giving users suid/sgid permission from home directories, /var, /tmp, etc. • Find and track suid programs. • Make sure you know the contents of all .rhosts files. • Use shadow passwords and PAM authentication.

  28. Local Kernel Security

  29. Kernel Security • Unless you intend to run this system as a firewall, do not enable firewall, ip masquerading and icmp masquerading when compiling a new kernel. • Use /dev/random and /dev/urandom for highly random number applications.

  30. Linux Network Security

  31. Watch Out For Sniffers • Packet sniffers are easy to do, and can be easily used to get passwords from apps that transmit password in the clear. • Watch out for • telnet • ftp • su • Pop3 accounts • All other programs that send passwords in the clear • Make it a practice to only use encrypting programs • ssh • stelnet

  32. Sign Your Communications • Don’t allow a hacker to steal your identity • Sign your communications • MD5 • PGP

  33. Think Like A Hacker • Run port scanners such as Satan, ISS and other network scanners. • SATAN:http://www.ibiblio.org/pub/packages/security/Satan-for-Linux/ • ISS • Abacus:http://www.psionic.com/abacus • Saint:http://www.wwdsi.com/saint/ • Nessus:http://www.nessus.org/ • Test firewalls with services from http://grc.com/ and HackerWacker (http://208.179.251.103/).

  34. Test Your Paswords • Make sure they are not easy to guess • John the Ripper:http://www.openwall.com/john/

  35. Characterize Your System • Constantly monitor your system for intruders modifying your file system • Tripwire:http://www.tripwire.com/ • Snort:http://www.snort.org/

  36. Secure Linux Solutions

  37. Linux Vendor Security Info • Mandrake:http://www.linux-mandrake.com/en/security/ • Caldera:http://www.caldera.com/support/security/ • Debian:http://www.debian.org/security/ • SuSE:http://www.suse.de/de/support/security/ • RedHat:http://www.redhat.com/mailing-lists/linux-security/ • TurboLinux:http://www.turbolinux.com/security/

  38. Secure Linux Distributions • Bastille Linux:http://www.bastille-linux.org/ • NSA Security-Enhanced Linux:http://www.nsa.gov/selinux/

  39. Linux Security Information • Linux Security HOWTO: http://www.linuxdoc.org/HOWTO/Security-HOWTO.html • Linux Administrators' Security Guide:http://www.securityportal.com/lasg/ • Linux Security Knowledge Base:http://www.securityportal.com/lskb/ • Linux Security Archive (mailing list):http://www.sonic.net/hypermail/security/ • Linux Firewall and Security Site:http://www.linux-firewall-tools.com/linux/ • Linux Security.com:http://www.linuxsecurity.com/ newsgroup: comp.os.linux.security:news:comp.os.linux.security

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