slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
Telecommunications Networking II PowerPoint Presentation
Download Presentation
Telecommunications Networking II

Loading in 2 Seconds...

play fullscreen
1 / 9

Telecommunications Networking II - PowerPoint PPT Presentation

  • Uploaded on

Telecommunications Networking II. Lecture 41d Denial-of-Service Attacks. Network Denial-of-Service Attacks and Other Network-Application-Based Attacks. Network Denial-of-Service Attacks. Attacker’s objective To interrupt or reduce the quality of services…as experienced by legitimate users

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Telecommunications Networking II' - rose-stokes

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Telecommunications Networking II

Lecture 41d

Denial-of-Service Attacks

network denial of service attacks and other network application based attacks

Network Denial-of-Service AttacksandOther Network-Application-Based Attacks

network denial of service attacks
Network Denial-of-Service Attacks
  • Attacker’s objectiveTo interrupt or reduce the quality of services…as experienced by legitimate users
  • Many attacks have innocent counterparts (e.g., someone sends me a very large E-mail attachment, and blocks my access to other messages)
network denial of service attacks1
Network Denial-of-Service Attacks
  • The “SYN” Flooding attack:-In TCP, one establishes a connection by sending a synchronization (SYN) message to the host one wishes to communicate with-The attack: send a large number of SYN messages (with phony source addresses) to a host. This overloads the buffer in the host that keeps track of TCP connections (and half-connections) in progress

TCP SYN Flooding Attack


SYN(1024), ACK(501)

No acknowledgement of prior SYN segment….

...More new SYN segments

More SYN acknowledgements ...

network denial of service attacks2
Network Denial-of-Service Attacks
  • The “SYN” Flooding attack:-Some protection can be gained by configuring networks so that they will not accept IP packets from external (to the network) sources whose source addresses are internal to the network; and which will not allow internal sources to send IP packets to external destinations if the source addresses used are not internal addresses
sequence number attacks
Sequence Number Attacks
  • Disable a host that is trusted by the target (intended victim) machine
  • Initiate a TCP connection by impersonating the disabled host (I.e., use it’s IP address) and sending a SYN message.
  • Guess the initial sequence number that the target system will use; and respond with an acknowledgement.

TCP Sequence Number Attack


SYN(800), ACK(501)


ACK(801), data

ACK( )

ACK(801), FIN(1012)


ACK(1013), FIN(800)


Ref: “Firewalls and Internet Security”

other network based attacks
Other Network-based Attacks
  • See Cheswick and Bellovin Chapter 2
  • Many network-based attacks are caused by the lack of strong authentication of sources (e.g., it is easy to impersonate another machine by using its IP address) and lack of encryption on IP network links