It involves some modification of data stream and can be sub divided into four categories
- Masquerade – It takes place when one entity pretends to be another entity
- Replay – It involves passive capture of data unit and its subsequent retransmission to produce unauthorized effect.
- Denial of service – The denial of service prevents or inhibits the normal use or management of communication facilities
- Modification of message – It simply means that some portion of legitimate message is altered or the message are delayed or reordered to produce unauthorized effect.