Targeted Break-in, DoS, & Malware attacks (II)

1. Targeted Break-in, DoS, & Malware attacks (II) (February 24 2014) © Abdou Illia – Spring 2014

2. Learning Objectives • Discuss DoS attacks • Discuss Malware attacks

3. Denial of Service Attacks

4. SYN SYN SYN 3 1 2 SYN/ACK SYN/ACK SYN/ACK ACK ACK ACK TCP opening and DoS Server • For each TCP connection request (SYN), server has to: • Respond to the request (SYN/ACK) • Set resources aside in order respond to each data request . . . . Waiting for request from Computer 1 Waiting for request from Computer 2 Waiting for request from Computer 3 . . .

5. Web Server configuration

6. Attacker’s Home Network Denial of Service (DoS) • What resources the web server would use to respond to each of the HTTP requests it receives? • What could be the consequences of the web server being invaded by too much requests from the attacker?

7. Denial of Service (DoS) Attack • Attack that makes a computer’s resources unavailable to legitimate users • Types of DoS attacks: • Single-message DoS • Flooding DoS • Distributed DoS

8. Single-message DoS attacks • First kind of DoS attacks to appear • Exploit weakness in the coding of operating systems and network applications • Three main single-message DoS: • Ping-of-Death • Teardrop • LAND attack

9. Total Length (16 bits) Flags Fragment Offset (13 bits) Ping of Death attacks • Take advantage of • Fact that TCP/IP allows large packets to be fragmented • Some network applications & operating systems’ inability to handle packets larger than 65536 bytes • Attacker sends IP packets that are larger than 65,536 bytes through IP fragmentation. • Ping of death attacks are rare today as most operating systems have been fixed to prevent this type of attack from occurring. • Example of PoD code and vulnerable Operating Systems: • http://insecure.org/sploits/ping-o-death.html • Fix • Add checks in the reassembly process or in firewall to protect hosts with bug not fixed • Check: Sum of Total Length fields for fragmented IP is < 65536 bytes Fragment offset: identify which fragment this packet is attached to.Flags: indicates whether packet could be fragmented or not

10. Total Length (16 bits) Flags Fragment Offset (13 bits) Teardrop attacks • Take advantage of IP fragmentation • Attacker sends a pretend fragmented IP packet • But Fragment Offset values are not consistent • Earlier operating systems* and poorly coded network applications crash because • Unable to reassemble the packet due to missing fragments Pretend fragmented IP packet Frag 1 Frag 2 Frag 4 Attacker Victim * Win 3.1, Win 95, Win NT, and Linux prior to 2.163

11. LAND attacks • First, appeared in 1997 • Attacker uses IP spoofing with • source and destination addresses referring to target itself. • Back in time, OS and routers were not designed to deal with this kind of loopback • Problem resurfaces recently with Windows XP and Windows 2003 Server

12. Summary Questions 1 • Do DoS attacks primarily attempt to jeopardize confidentiality, integrity, or availability? • Which of the following DoS attacks takes advantage of IP fragmentation? • LAND attack • Teardrop • Ping of Death • None of the above • In which of the following DoS attacks the attacker makes use of IP spoofing? • LAND attack • Teardrop • Ping of Death • None of the above

13. Flooding DoS Attacks • Flood a target with a series of messages in an attempt to make it crash • Main types of flooding DoS attacks: • Flooding with regular requests • SYN flooding • Smurf flooding • Distributed DoS

14. Flooding with regular request • Open cmd and type: ping /? • Show the –l option • Show the following video about using ping –l in a possible attempt to flood the allrecipes.com website. • Youtube: How To DOS a Website

15. SYN Flooding • Attacker sends a series of TCP SYN opening requests • For each SYN, the target has to • Send back a SYN/ACK segment, and • set aside memory, and other resources to respond • When overwhelmed, target slows down or even crash • SYN takes advantage of client/server workload asymmetry SYN SYN SYN SYN SYN Attacker Victim

16. Smurf Flooding DoS • Attacker uses IP spoofing • Attacker sends ping / echo messages to third party computers on behalf of the target • All third party computers respond to target

17. Distributed DoS (DDoS) Attack • Attacker hacks into multiple clients and plants handler programs on them. Clients become bots or intermediaries • Attacker sends attack commands to handlers which execute the attacks • First appeared in 2000 with Mafiaboy attack against cnn.com, ebay.com, etrade.com, yahoo.com, etc. Attack Command DoS Messages Bots Attack Command Server Handler Attacker Attack Command DoS Messages Link to how to deal with DDoS (by Cisco)

18. Distributed DoS (DDoS) Attack

19. Distributed DoS (DDoS) Attack

20. Summary Questions 2 • Describe SYN flooding. • Describe Smurf flooding • What is a DDoS attack? • What is a Handler program?

21. Malware Attacks

22. Malware attacks • Types of malware: • Viruses • Worms • Trojan horses • Logic bombs

23. Virus • Code/Program (script, macro) that: • attaches to files • Spreads by user actions (floppy disk, flash drive, opening email attachment, IRC, FTP, etc), not by themselves. • Symptoms: • Annoying actions when the virus is executed: hog up memory, crash the system, drives are not accessible, antivirus disabled, etc. • Performing destructive actions when they are executed: delete files, alter files, etc.

24. Viruses • Could be • Boot sector viruses: attach themselves to files in boot sector of HD • File infector viruses: attach themselves to files (i.e. program files and user files) • Polymorphic viruses: mutate with every infection (using encryption techniques), making them hard to locate • Metamorphic viruses: rewrite themselves completely each time they are to infect new executables* • Stealth: hides itself by intercepting disk access requests by antivirus programs. Request by antivirus The stealth returns an uninfected version of files to the anti-virus software, so that infected files seem "clean”. Stealth OS * metamorphic engine is needed

25. Worm • Does not attach to files • A self-replicating computer program that propagate across a system • Uses a host computer’s resources and network connections to transfer a copy of itself to another computer • Harms the host computer by consuming processing time and memory • Harms the network by consuming the bandwidth Question: Distinguish between viruses and worms

26. Trojan horse • A computer program • That appears as a useful program like a game, a screen saver, etc. • But, is really a program designed to damage or take control of the host computer • When executed, a Trojan horse could • Format disks • Delete files • Open TCP ports to allow a remote computer to take control of the host computer (Back Door) • NetBus and SubSeven used to be attackers’ favorite programs for target remote control

27. Trojan horse NetBus Interface

28. Logic bomb • Piece of malicious code intentionally inserted into a software system • The bomb is set to run when a certain condition is met • Passing of specified date/time • Deletion of a specific record in a database • Example: a programmer could insert a logic bomb that will function as follow: • Scan the payroll records each day. • If the programmer’s name is removed from payroll, then the logic bomb will destroy vital files weeks or months after the name removal.

29. Summary Questions 3 • Distinguish between a virus and a worm • What kind of malware is a malicious program that could allow an attacker to take control of a target computer? • What kind of malware could harm a host computer by consuming processor time and random access memory?