-SHAMBHAVI PARADKAR TE COMP

 PORT SCANNING.  DENIAL OF SERVICE(DoS). - DISTRIBUTED DENIAL OF SERVICE(DDoS). REFER Pg.637 & Pg.638

 The act of systematically scanning a computer's ports.  Since a port is a place where information goes into and out of a computer, port scanning identifies open doors to a computer.  Port scanning has legitimate uses in managing networks, but port scanning also can be malicious in nature if someone is looking for a weakened access point to break into your computer.

 There is no way to stop someone from port scanning your computer while you are on the Internet because accessing an Internet server opens a port, which opens a door to your computer.

 It is not an attack, but mean for a cracker to detect system’s vulnerabilities to attack.  It is automated that involves a tool that creates an IP connection to a specific port or range of ports.  There are tools that perform subsets of their functionality.

 1] nmap (from  It is a versatile open source utility for network exploration & security audition.  When pointed at a target,it will determine what services are running including application names & versions.  It can identify the host OS and provides information about defences.  It does not exploit any known bugs.

2] nessus (from  It has a database of their of bugs and their exploits.  It can scan a range of systems, determine the services running on those systems, and attempt to attack all appropriate bugs.  It generates reports about the results.  It does not perform the final step of exploiting the found bugs what a cracker could.

 Since port scanning are detectable they are frequently launched from zombie systems.  Such systems are previously compromised, independent systems that are serving their owners while being used for neferious purposes including denial of services attacks and spam relay.  Zombies make crackers difficult to prosecute since determining the source of attacks & the person that launched is challenging.

 These are aimed at disrupting legitimate use of a system or facility.  It is a type of attack on network that is designed to bring network to the knees by flooding it with useless traffic.  It is impossible to prevent denial of service attacks.

 It is more difficult to prevent & resolve.  These attacks are launched from multiple sites at once, towards a common target typically by zombies.  These attacks are mostly associated with blackmail attempts.  Ex. A successful advertising campaign that generally increases traffic to a site.

 Write a short note on port scanning. Give examples.  Explain on denial of service.