IN THE NAME OF ALLAH listen , in the security world , every thing but the objective must disallowed ,it is very important to determine which service and ports are in use and who use them and why he use them .
any thing else is a security defect "The system must serves aviable resources and preserves them" , icmp can really used in a type of attack called DOF : Danial Of Service and this can interrupt the service from legitimate users and you must know this the hanged system must consider to be untrusted okay I will speek about the Important ICMP message Types : 1] Echo requist(8)/echo replay(0) which test whether a host is active or not , and this can used in a smurf attacks with a spoofed source address to fload a target 2] Dstination unreachable(3) this mean --a>from router :donot know the route to the target , and can use to obtain info about the firewall "It is not send by a hacker but it awaited from him" 3]Source Quench (4) it mean Packet arriving to fast and requist slow down , It can be also used in DOS attack 4]Redirect (5) mean use another router to route this packets , can used in sniffing [Non-text portions of this message have been removed]
