Router firewall and validating identity
Nmap performs a ping sweep to identify hosts that are active on the network and then proceed to identify what services respond.You can also check the configuration of firewalls and access policies for critical systems.If you execute Nmap with its default settings, and assuming you have root privileges, Nmap performs a SYN scan: Nmap sends a SYN to all of the ports listed in its services file (over 1,000 ports) and looks for a SYN/ACK response.If it gets a response, it assumes that the port is open and immediately sends a RST (reset) to close the connection and then move on to the next port to be tested.Starting Nmap 5.21 ( Interesting ports on 172.16.1.3: Not shown: 1707 closed ports PORT STATE SERVICE 135/tcp open msrpc 139/tcp open netbios-ssn 445/tcp open microsoft-ds 3389/tcp open ms-term-serv MAC Address: 00:1A:92:0A:62: B1 (Asustek Computer) Nmap done: 1 IP address (1 host up) scanned in 2.226 seconds Scanning for UDP ports is handled differently.Because UDP doesn't have a handshake process like TCP, the UDP packet must be crafted in a manner that causes the operating system to respond back.Nmap uses an "operating systems normal" response to a valid connection request or "tear down" response to determine whether a port is open (listening and responding) or if it is not enabled.A typical TCP connection follows a three-way handshake to set up communications.
One thing is certain about security auditing tools: The power and sophistication of tools that auditors have at their disposal increase exponentially every year.
Not only are the authors of these tools truly brilliant individuals (and some scary ones, too), they have also helped the security community significantly through the automation of advanced testing techniques.
If you attend Blackhat, Def Con, or other security conferences, you can see the latest and greatest additions to this growing list of powerful applications.
X OS details: Cisco Catalyst C2950 or 3750G switch (IOS 12.1 - 12.2) Network Distance: 1 hop Service Info: OS: IOS; Device: router Nmap done: 1 IP address (1 host up) scanned in 18.877 seconds Nmap provides several ways to mask your identity when scanning.
One of the more popular mechanisms is through an idle scan.