An Introduction to UNIX Security

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Transcript An Introduction to UNIX Security

An Introduction to
UNIX Security
A Presentation by
Trey Evans
[email protected]
www.bestican.net
Linux or UNIX?
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System V
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BSD
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Linux, AIX, HP-UX, Solaris
Net, Open, Free
AT&T
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SCO, IRIX, Solaris
Out of the Box Security
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Very limited deployment options
Custom tailoring always the best option
Expensive to migrate
Often easy to monitor
Kernel Security
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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
Network Security
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ipchains, iptables, “routes”
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Tells machine what to do with what packets under
certain circumstances
Set up *nix box as a router / firewall / both
Tame user privileges
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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
Email Security
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Sendmail
Qmail
www.google.com
Begin Fun Stuff
Penetration
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Physically insert your machine into the
target’s network
Bypass perimeter security
Control router or outer most point
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“Edge devices”
Physical Insertion
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Basically, obtaining an IP on the system
Man in the middle
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Easiest way – Wireless
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Wireless – airjack userland utilities
Wired – spoof MAC, auth as legit user
bestican.net/wifi/pres.pdf
DHCP? IP addressing scheme?
Bypass security
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Portscan looking for services
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Box on inside?
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Test firewall rules using packet crafting
See illustration
DoS or DDoS
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nmap stealth mode (-s) or OS discover (-O)
Lame.
Google exploits for firewall
Outermost Device
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Root access on gateway or firewall or router
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Gives access to ALL packets on network
Redirect at will
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Change IP table
Change message or headers
Sniff passwords
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Write them down, you’ll need them later
Discovery
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Ask “what’s the payload?”
Portscan
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Rootkit
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nmap, NetCat, nmap for X
Requires root on an internal box
Must be well hidden
Exploit scanner
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Don’t get caught
Hardware may skew results
Morph
Elevate Privileges
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Local access is root access
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Based on boot loader, usually
Google.com
Doesn’t insert NFS folders into hierarchy
Exploits tailored to machine
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Cool CC example
Cool passwd example
Historic Exploits
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FTPD buffer overflow
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Sendmail remote call
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Widespread, FTPD installed by default often
Gave root FTP access
Auth as root
Send mail as anyone, read anyone’s mail
evil.c
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Not a big threat (unless hosting)
Local access needed
Demo?