Review Exam 2 Spring 2013

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

Unobtrusive Information Collection Sending packets into a network is “noisy” Need to do unobtrusive info gathering, first, by Visiting target corporate website for Employees’ names and emails Officers names and organizational structure, etc. Reading trade press (often online & searchable) for Info about products under development Firms’ financial prospects, etc. Searching U.S. EDGAR* system online for Ownership, shareholder information, etc. Searching the Whois database at: NetworkSolutions.com/whhois/index.jsp, internic.net/whois.html, etc. * Electronic Data Gathering, Analysis, and Retrieval

Host Scanning Ping scanning Objective: identify IP addresses of active hosts Pinging individual hosts Ping scanning Pinging a range of IP addresses IP scanning software: fping, gping, Ping Sweep, Pinger SYN/ACK scanning used when firewall configured to block pinging from outside

Network Scanning Objective: understand a network internal structure including routers, firewalls location Also called network mapping Main tools used Tracert (in Windows) or Traceroute (in Linux) Network scanning software, e.g NetScanner

Port Scanning Port Scanning Most break-ins exploit specific services/applications Service Default Port www 80 FTP 21 SMTP 25 Scan target for open ports Send SYN segments to a particular port number Observe SYN/ACK or reset (RST) responses

Fingerprinting Determining specific software run by target Identify a particular operating system or application program and (if possible) version For example, Microsoft Windows 2000 Server For example, BSD LINUX 4.2 For example, Microsoft IIS 5.0 Useful because most exploits are specific to particular programs or versions

Active vs. Passive fingerprinting Active Fingerprinting Send odd messages and observe replies Different operating systems and application programs respond differently Active fingerprinting may set off alarms Attackers usually use rate of attack messages below IDSs volume thresholds Passive Fingerprinting Read headers (IP-H, TCP-H, etc.) of normal response messages e.g. Windows 2000 uses TTL = 128 and Window Size = 18000 Passive Fingerprint difficult b/c Admin could change default values Time To Live (8 bits) Protocol (8 bits) 1=ICMP, 6=TCP,17=UDP Window Size (16 bits)

Fingerprinting by reading banners Many programs have preset banners used in initiating communications Using telnet or FTP to connect to a server could display the banner

Summary Questions 1 (cont.) In preparing his attack, the attacker sent normal HTTP requests to a web server. Then, he spent some time analyzing the protocol-related information in the response received from the web server in order to determine what software are installed on the web server. Which of the following did the attacker do? Active learning Network scanning Passive fingerprinting None of the above

Password guessing Brute force Generating possible password combinations by changing one character at a time If password is 4 decimal numbers Start with 0000; next try 0001; then 0002; etc. How many possible combinations? ___________ If password is 6 alphabetical characters, how many possible combinations? _____________ Brute force password cracking software available

Summary Questions 2 (cont.) Assume that a password is 2 decimal number long. What is the maximum number of passwords that an attacker would have to try in order to crack the password? 4 67108864 1024 None of the above How much time (in minutes) will it take to crack the password if it requires 1.2 second to try each password? Answer: a maximum of ______ minutes.

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

TCP opening and DoS Server 1 . SYN Waiting for request from Computer 1 SYN/ACK ACK 2 SYN Waiting for request from Computer 2 SYN/ACK ACK 3 SYN Waiting for request from Computer 3 SYN/ACK ACK . 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

Denial of Service (DoS) Attacker’s Home Network 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?

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

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

Fragment Offset (13 bits) 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

Teardrop attacks Take advantage of IP fragmentation 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

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

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?

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

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

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

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)

Distributed DoS (DDoS) Attack

Distributed DoS (DDoS) Attack

Malware Attacks

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

Virus Code/Program (script, macro) that: attaches to files Symptoms: 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.

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

Question: Distinguish between viruses and worms 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

Trojan horse A computer program When executed, a Trojan horse could 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

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.