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Linux: Networking & Security

Linux: Networking & Security. Feng Gao 104504 2000-08-31. Objective (1). Give an overview of the networking capacities of the Linux OS Networking protocols Capacity for file sharing & printing Capacity for Internet/Intranet services Capacity for remote execution of application

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Linux: Networking & Security

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  1. Linux:Networking & Security Feng Gao 104504 2000-08-31

  2. Objective (1) • Give an overview of the networking capacities of the Linux OS • Networking protocols • Capacity for file sharing & printing • Capacity for Internet/Intranet services • Capacity for remote execution of application • Capacity for acting as network interconnection • Capacity for network management

  3. Objective (2) • Talk about some security tools for Linux network • Monitoring tools • Network services • System integrity • Management & limitation

  4. Brief Introduction of Linux OS • A Unix like operating system • Completely open source code • no royalty or licensing fees • the source code can be modified to fit users’ needs • Fast, powerful, and extremely stable • Cross hardware and platform • Tons of application software • Created by and for the Internet

  5. Why Linux is a choice for network • Cheap & portable • Ideal for many small to medium businesses • Open source code • Tons of applications are freely available • Modifiable whenever/wherever needed • Robustness

  6. Who uses Linux? Besides ISPs and other Web companies, the following companies had some Linux servers installed in 1997. • Ford Motor Co. • NASA • Disney • General Electric • IRS • UPS • NASDAQ • Boeing • many leading US Universities • Used for gateways, routers, file and print servers, database servers, computation servers, development servers, CAD, besides being used as Web servers.

  7. Part I Linux Networking

  8. Network protocols supported by Linux • TCP/IP • IPv6 ( IP version 6 ) • IPX/SPX • AppleTalk Protocol • WAN networking Protocols • Isdn4linux • PPP, SLIP, PLIP • ATM • More 

  9. File sharing and printing • Sharing with Apple environment • using AppleTalk family protocols ( NetaTalk) • Sharing with Windows environment • using Samba ( an implementation of SMB protocol) • Sharing with Novell environment • using IPX/SPX • Sharing with Unix environment • using NFS ( Network File system)

  10. Internet / Intranet services • Mail • Mail Servers ( eg.Sendmail, smail, qmail, etc.) • Remote access to mail (POP, IMAP) • Fetchmail • Web Servers • Apache • Stable, Robust • Yahoo, Altavista, Geocities, Hotmail are based on this server

  11. Internet/Intranet services (cont’) • Web Browsers • Netscape Navagator, Mozilla , lynx, etc. • FTP servers & clients • News service • Domain Name System ( DNS ) • NIS ( Network Information Service )

  12. Remote execution of application • Telnet • Use a remote computer as if just at the site • Remote commands • Execution of a command on a remote machine • The X window system • The X server controls the display and I/O • The X client do the real computing work • VNC ( Virtual Network Computing) • eg. Execute in a Windows machine and output displayed in a Linux machine

  13. Acting as Network Interconnection • Bridge • Router • Firewall • Proxy Server • IP Masquerade • Load Balancing • Traffic Shaping • Port Forwarding • Virtual private networks

  14. Network Management • Network management applications • Webmin • Linuxconf • SNMP (Simple Network Management Protocol ) • allows for remote monitoring and configuration of routers, bridges , network cards, switches …

  15. Part II Security tools for Linux network

  16. Monitoring tools • Scan to determine if the machine is vulnerable to a specific exploit on that server • Connect to target machine on all ports they can • Help to fix the found problems • Examples: • SATAN ( Security Administrator’s Tool for Analyzing Networks ) • ISS( Internet Security Scaner ) • SAINT ( updated version of SATAN ) • Nessus, xSid, Logcheck, PortSentry

  17. Network Services • Problem • The more services the system offers, the more places for attackers to find a hole

  18. Network Services (cont’) • Strategy • Disable or remove services not needed • Use tcp_wrappers to wrap all the TCP services • Use SSH to replace old, insecure remote programs such as telnet, rlogin, rdist, rcp • SSH • A secure login program that revolutionized remote management of networks hosts over the Internet • A powerful program that uses strong cryptography for protecting all transmitted confidential data

  19. System integrity • Problem • A typical Linux server handles about 30,400 files • In its busy times administrators can’t check the integrities of all system files • A cracker can easily install or modify some files

  20. System Integrity ( cont’ ) • Security tools • Tripwire • Tripwire ASR ( Academic Source Release ) Create a database first  Check the integrity of a system at any time  Compare the current system and the stored database  Find if malicious changes exist

  21. Management & Limitation • GnuPG • A tool for secure communication and data storage • Can be used to encrypt data and create digital signatures • Quota • A system administration tool for monitoring and limiting users’ and groups’ disk usage • With quota, the users are forced by the system administrator to not consume unlimited disk space on a system

  22. Summary • The network capacities of Linux OS : • Support of many network protocols • File sharing and printing • Internet / Intranet Services • Remote execution of application • Acting as network interconnection • Network managemet We’ve talked about:

  23. Summary • Some security tools for Linux network: • Monitoring tools • Network services • System integrity • Management & Limitation Also talked about:

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