Attacks and Malicious code - Introduction to Network Security - Lecture Slides, Slides of Network security

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Attacks and Malicious code

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Attacks and Malicious Code

• Denial of Service (DoS)
  • SYN flood
  • Smurf
  • Distributed DoS
• Spoofing
  • IP spoofing
  • ARP poisoning
  • Web spoofing
  • DNS spoofing

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Attacks and Malicious Code

• Attacks on encrypted data
  • Weak keys
  • Birthday attack
  • Dictionary attack
• Software exploitation
  • Malicious software (virus and worm)
  • Back door
  • Logic bombs
• Countermeasures

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Why we need security?

Good news: Your employees and partners can now access your critical business information

Bad news: Your employees and partners can now access your critical business information

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Some Statistics

Financial loss reported due to attacks ~ $500 million Not every one reports loss due to attacks

Type of attack Percentage Virus 85% Denial of Service 40% Intrusion 40%

Internet as source of attack: 74%

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Main issues

• Security never stops
• New threats constantly emerge
• Security is concerned with risk management
• Existing security products are weakly integrated
• Lack of well understood security policy
• Too much reliance on technology alone for security

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Common Attacks

• SYN flooding attack
  • This exploits how the 3-way handshake of TCP services for opening a session works.
  • SYN packets are sent to the target node with incomplete source IP addresses
  • The node under attack sends an ACK packet and waits for response
  • Since the request has not been processed, it takes up memory
  • Many such SYN packets clog the system and take up memory
  • Eventually the attacked node is unable to process any requests as it runs out of memory storage space

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Land attack

• Similar to SYN attack
• Uses the target address as the source address as well
• Causes an infinite loop under the SYN/ACK process

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Smurf attack

• A brute force DOS attack and thus a non-OS specific attack
• A large number of PING requests with spoofed IP addresses are generated from within the target network
• Each ping request is broadcast, resulting in a large number of responses from all nodes on the network
• Clogs the network and prevents legitimate requests from being processed

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Ping of death

• The hacker sends an illegal echo packet with more bytes than allowed, causing the data to be fragmented. This causes the data to be stored causing buffer overflows, kernel dumps, and crashes
• This was made possible by some Windows OSs allowing non-standard ICMP (Internet Control Message Protocol) messages to be generated
• Maximum ICMP packet size is 65507 bytes. Any echo packet exceeding this size will be fragmented by the sender and the receiver will try to reconstitute the packet, when overflow would occur

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UDP-flood attack

• Denial of service variant
• Connects the target machine’s chargen and echo services to create an infinite loop between two or more UDP services
• Connectivity to the network is sufficient, no network account required for this attack

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IP Spoofing

• Exploits trust relationships between routers
• This is a difficult attack to launch since the communication set up is based on an initial sequence number for packets. Systems no longer use numbers sequentially. Identifying the algorithm used for numbering packets during set up is important.

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ARP Poisoning

• ARP = Address Resolution Protocol
• ARP is used by routers extensively to find the destination node. Routers have IP addresses (32-bits). In order to deliver the packet to the destination node, the router broadcasts the IP address of the destination and obtains the MAC address (48-bits).