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Hacking Linux

Hacking Linux. Based on Hacking Linux Exposed Hatch, Lee, and Kurtz ISBN 0-07-212773-2. Looking into Linux. Linux security overview Proactive measures and recovering. Stages of hacking – again. Mapping your machine and network Social Engineering, Trojans, and other tricks

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Hacking Linux

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  1. Hacking Linux Based on Hacking Linux Exposed Hatch, Lee, and Kurtz ISBN 0-07-212773-2

  2. Looking into Linux Linux security overview Proactive measures and recovering

  3. Stages of hacking – again • Mapping your machine and network • Social Engineering, Trojans, and other tricks • Physical attacks • Attacking over the network • Abusing the network itself • Elevating user privilege • Password cracking • Maintaining access

  4. Server issues and vulnerabilities • Mail and ftp • Web servers and dynamic content • Access control and firewalls

  5. Linux security overview • Porque • You are easy • You can be used as anonymous access • You are Linux and thus open source • The OS source is available • But the developers are self-policing – developer culture and Bugtraq • Access control methods • Password security • Controls on users • Privileged ports • Virtual memory gets reclaimed

  6. Proactive measures and recovering • Proactive measures • Insecurity scanners – finding your own weakness • Scan detectors – is someone eyeballing you? • Hardening your system • Log file analysis • File system integrity checks • Recovering from being hacked • Detecting if you have been hacked • What to do after a breakin

  7. Mapping your machine and network • Public domain looking • Online searches • Whois databases • Ping sweeps • DNS issues • Traceroutes • Port scanning • OS detection • Active stack fingerprinting • Passive stack fingerprinting

  8. Mapping, continued • Enumerating RPC services • What authentication level is used • What services – NFS, NIS, other PRC • NFS file sharing • What is exportable – and to what users • SNMP possibilities • Network insecurity scanners • Canned stuff that combines all these approaches

  9. Social Engineering, Trojans, and other tricks • Social engineering • Trojan horses • Viruses and worms • IRC backdoors

  10. Physical attacks • Attacking the office • Sneaky pete installs something • Boot access is root access • Boot passwords are in the flash ROM • Setup helps a little bit • Encrypted filesystems

  11. Attacking over the network • Using the network itself • TCP/IP • The public phone system • Default or bad configurations • NFS mounts • Netscape defaults • Squid • X-Windows system

  12. TCP/IP • Structure (header and function) • TCP • Flag bits (Urgent, Ack, Push, Reset, Syn, Fin) • UDP – less structure and functionality • ICMP – Control messages – many hacking possibilities • IP – Underlies these three protocols – host-to-host

  13. The public phone system • Modem attacks • Wardialing – mechanized dialing used to find modems • Attacks on modem internal protocols – Hayes not-so-smart Modem • Idea was to shut off sound, store a new number, disconnect and redial Moldavia • Countermeasures • One-time-pad login modules • Passwording • Biometrics

  14. More network attacks • Default passwords and password guessing • Sniffers • How they work • Common versions • Vulnerabilities • Buffer overflows • Vulnerable services • Vulnerable scripts • Unnecessary services and detecting them • Using netstat, lsof, nmap • How to turn them off – inetd.conf

  15. Abusing the network itself • DNS Exploits • Routing issues • Advanced sniffing and session hijacking • Hunt • Dsniff • Man-in-the-middle attacks • Denial of service (DoS) attacks • Floods • TCP/IP attacks

  16. More abuse and countermeasures • Abusing trust relationships • Implementing egress filtering

  17. Elevating user privilege • Users and privileges • Elevation of privilege • Trusted paths and trojan horses • Password storage and use • Special purpose groups and device access • Sudo • Suid programs • Hacker suids on mounted file systems • Countering poor programming

  18. Password cracking • How they work • More advanced algorithms • Cracking programs • Shadow passwords • Pluggable modules, etc.

  19. Maintaining access • Using the r commands, rsh, rexe, etc. • Passwordless access using ssh • Network accessible root shells • Trojaned system programs • Back doors • Trail hiding • Kernel hacks

  20. Remote access methods - Unix • Primary methods • Exploiting a listening service (TCP/IP) • System must be running services listening on some port • First enumerate, then specific exploit for that service • Using source routing to cross firewall or router • Router must have source routing disabled, or at least protected • User-triggered traps • Example: browsing as root and encountering malicious code • Exploiting system with network interface in promiscuous mode • Sniffer can sniff a malicious packet that was put there to catch any victim

  21. Brute force attacks • Password attacks • These can use any service that uses a logname/password for access • Many utilities exist for automating • Countermeasures are improved password analyzers, delay in login on incorrect passwords, detecting repeated login attempts • User password education – don’t use same password everywhere • Data driven attacks • Buffer and stack overflows work because of weak C libraries • Basic idea is to send an “egg” with code that goes on stack (used for local variables and return address)

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