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An Introduction to UNIX Security

An Introduction to UNIX Security. A Presentation by Trey Evans trey@bestican.net www.bestican.net. Linux or UNIX?. System V Linux, AIX, HP-UX, Solaris BSD Net, Open, Free AT&T SCO, IRIX, Solaris. Out of the Box Security. Very limited deployment options

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An Introduction to UNIX Security

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  1. An Introduction to UNIX Security A Presentation byTrey Evans trey@bestican.net www.bestican.net

  2. Linux or UNIX? • System V • Linux, AIX, HP-UX, Solaris • BSD • Net, Open, Free • AT&T • SCO, IRIX, Solaris

  3. Out of the Box Security • Very limited deployment options • Custom tailoring always the best option • Expensive to migrate • Often easy to monitor

  4. Kernel Security • Remove any drivers not used • If the user needs them, he/she can add them at boot time • Prevents unstable drivers from causing hiccups when called • Eliminates possibility of attacker exploiting weak driver or combination of drivers

  5. Network Security • ipchains, iptables, “routes” • Tells machine what to do with what packets under certain circumstances • Set up *nix box as a router / firewall / both • Tame user privileges • No need for users to be able to change IP • Keep users from enabling promiscuous mode • Keep users from enabling second network card • Perhaps disable user access to usbhci

  6. Email Security • Sendmail • Qmail • www.google.com

  7. Begin Fun Stuff

  8. Penetration • Physically insert your machine into the target’s network • Bypass perimeter security • Control router or outer most point • “Edge devices”

  9. Physical Insertion • Basically, obtaining an IP on the system • Man in the middle • Wireless – airjack userland utilities • Wired – spoof MAC, auth as legit user • Easiest way – Wireless • bestican.net/wifi/pres.pdf • DHCP? IP addressing scheme?

  10. Bypass security • Portscan looking for services • nmap stealth mode (-s) or OS discover (-O) • Box on inside? • Test firewall rules using packet crafting • See illustration • DoS or DDoS • Lame. • Google exploits for firewall

  11. Outermost Device • Root access on gateway or firewall or router • Gives access to ALL packets on network • Redirect at will • Change IP table • Change message or headers • Sniff passwords • Write them down, you’ll need them later

  12. Discovery • Ask “what’s the payload?” • Portscan • nmap, NetCat, nmap for X • Rootkit • Requires root on an internal box • Must be well hidden • Exploit scanner • Don’t get caught • Hardware may skew results • Morph

  13. Elevate Privileges • Local access is root access • Based on boot loader, usually • Google.com • Doesn’t insert NFS folders into hierarchy • Exploits tailored to machine • Cool CC example • Cool passwd example

  14. Historic Exploits • FTPD buffer overflow • Widespread, FTPD installed by default often • Gave root FTP access • Sendmail remote call • Auth as root • Send mail as anyone, read anyone’s mail • evil.c • Not a big threat (unless hosting) • Local access needed • Demo?

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