Internet Worms: Methods, Countermeasures and Famous Incidents

1. Internet Worms: Methods, Countermeasures and Famous Incidents Presented by: Tran To Brian Tully

3. Worms Are Bad! • Damages • Lost productivity • Compromised information • Lost Money • Total billions of dollars per year • Worms and viruses cost $8 billion in Jan. 2003 alone

4. Worms Exploit Vulnerabilities • Systems have faults • Orange Book – de facto standard that rates the security of operating systems • Windows has a class D rating – minimal protection • Unix has a class C1 rating – discretionary security protection

5. Goals • Examine system vulnerabilities • Weak passwords • Trap doors • Buffer overflows • Famous Incidents • Morris, Code Red, Blaster, Slammer, Sasser • Countermeasures

6. What is a Worm? • Necessary Criteria • Replication • Self-contained • Multi-tasking system • For network worms – replication across communication links

7. Two Major Classifications • Host computer worms • Entirely contained in computer it is running on • Uses network only to propagate • Network worms • Multiple segments on different hosts • Uses network for several communication purposes

8. Worms Are Not Really Bad?! • By definition worms are not malicious • Simply a program that replicates • First used for network management • Took advantage of system properties • Malicious worms do the same

9. History of Worms • Term coined by John Brunner • 1970s novel “The Shockwave Rider” • Xerox Palo Alto Research Center (PARC) • John Schoch and John Hepps use worms for distributed computations • Prove useful but managing worms is difficult • Night worm crashes systems • Possible malicious uses realized

10. System Vulnerabilities • Worms attack availability, confidentiality and integrity • Exploit flaws in OS to replicate • Weak passwords • Trap Doors • Gain access to user accounts • Buffer Overflow • Gain root access

11. Password Attack • Brute force • Time consuming • Worms take advantage of weak passwords • Dictionary attack • List of commonly used passwords

12. Backdoor Attack • Usually undocumented feature that sidesteps security mechanisms • debugging • Maintenance • Easy access to system once discovered

13. Buffer Overflow • Buffer – contiguous allotted chunk of memory, such as an array • In C and C++ there is no bounds checking • Can write past end of a buffer • Spill into user space or OS space • Functions sprintf(), scanf(), gets(), strcpy() • Do not check that destination buffer is large enough • Buffer overflow attacks exploit this

14. Stack Overflow Attack • Buffer put on a stack • Maintains pointers • Subroutine Call • Parameters and return address pushed on stack • By entering long unchecked parameters, attacker can manipulate return address

15. Stack Overflow Attack • Attacker has two options • Inject attack code into return address • Gain root privileges • Change return address • Alter the path to point to malicious code

16. Countermeasures • Choose hard to guess passwords • Do not build backdoors • Write secure code • Use strncpy() instead of strcpy() to limit the side of the buffer • Bound checking compilers

17. Famous Incidents • Christmas Tree Worm • Attacked IBM in Dec. 1987 • Chain letter and Trojan horse • Drew Christmas tree on display  • Also forced computers to shut down 

18. Morris Worm • Released Nov. 2, 1988 • Purpose was to propagate • Attacked mail servers • Exploited holes in Unix • Trap door in Sendmail • Buffer overflow Finger Daemon • Overwrote 512 character buffer with 536 • Extra 24 characters executed as commands • Password Cracker

19. Morris Worm • Affected 6,000 systems • Consumed excessive system resources • Morris confessed to creating the worm out of boredom?! (I sleep when I’m bored, I don’t terrorize the nation) • Convicted in 1990 of violating 1986 Computer Fraud and Abuse Act • Fined $10,000 • Three years probation

20. Code Red • Affected more than 250,000 servers in July 2001 • Web servers running Microsoft’s Internet Information Server (IIS) • Checked port 80 and sent HTTP GET request to propagate • Exploited buffer overflow vulnerability of idq.dll

21. Code Red • First nineteen days • Looked for servers to infect • Defaced web pages requested by servers • Days 20-27 • Launched DDOS attack against the White House web site • Day 28 • Worm slept • Affected 750,000 servers total costing $2 billion

22. Blaster Worm • Released Aug. 11, 2003 • Affected Windows XP and Win2K systems • Purpose was to launch a DDOS attack against Microsoft’s windowsupdate.com • Spread Fast • Filtered ISPs for vulnerable systems • Exploited buffer overflow in Microsoft’s interface between Windows Distributed Component Object Model (DCOM) and Remote Procedure Call (RPC) • Gained root privileges through TCP/IP RPC packets • Prevented users from downloading patches

23. Blaster Worm • Used Port Scanning • Port 135 used by RPC • Deposit Trojan horse • Execute remote shell • Initiate TFTP request to download worm • Computer is now unwilling participant in DDOS attack • 1.4 million computers affected • Patch had been released a month prior

24. Slammer Worm • Fastest spreading worm • Doubled in size every 8.5 seconds • Affected 75,000 computers in 10 mins • Used random scanning • Selected IP addresses at random to infect and eventually found all vulnerable hosts • Simple fast scanner

25. Slammer Worm • Goal was to DDOS attack various hosts and slow down the Internet in general • Exploited buffer overflow vulnerabilities in Microsoft’s SQL Server • Transmitted TCP-SYN packet • Patch was available for six months before attacks occurred

26. Before the Slammer Worm hit

27. Thirty minutes later …

28. Sasser Worm • First noticed April 30, 2004 • Affected Windows XP and Win2K • Connected directly to open ports • Exploited buffer overflow in Microsoft’s local security authority subsystem service • Connected through TCP port 445 • Installed FTP server and transferred itself • Patch was available before release • Worm was possibly reverse-engineered from patch

29. Countermeasures • Update system • Download patches on a regular basis • Limit the amount of time a vulnerability can be exploited • Update anti-virus software on a regular basis • Latest software use heuristics • Identify code common to worms and variants • Configure firewall properly • Disable unnecessary services e.g. web and ftp servers • Build completely secure systems

30. Summary • Worms are here to stay • Individuals do not have much of a choice in systems • Security is dependent on developers of product • Forced to use insecure product knowing worms can attack it • Only solution is to not connect to the Internet, dig a hole and throw your router into the depths of the underworld

31. Possible Alternatives • With minimal effort a user can greatly increase the security of his or her inherently insecure system • Patches and updates • Minimal time between when vulnerability is discovered and when vulnerability is fixed • Firewall • Limit access to system so worms can’t get in to start • Simple procedures significantly reduce the extent to which worms can spread and cause damage

32. Questions?