5

When scanning with nmap using the -O or -A flag, nmap tries to determine the OS of the target machine.

Putting the question of why you would want to scan your own machine for OS aside, running OS scan on your own machine renders the message

Skipping OS Scan against 192.168.1.12 because it doesn't work against your own machine (localhost)

What is it that makes OS scan against your own machine impossible?

Zano
  • 520

2 Answers2

4

Because nmap does its work by performing various "side-channel attacks" on the packets that are received back from the requests it makes. It expects the packet to go through the normal path of 

nmap 
 -> OS 
   -> Driver
     -> Adapter (yours)
       -> Wire
         -> Adapter (theirs)
           -> Driver
             -> OS
               -> Application
             <- OS
           <- Driver
         <- Adapter (theirs)
       <- Wire
     <- Adapter (yours)
   <- Driver
 <- OS 
nmap

However when you are connecting to yourself any of the following optimizations could happen.

nmap 
 -> OS 
   -> Driver
     -> Adapter (yours)
       -> Driver
         -> OS
           -> Application
         <- OS
       <- Driver
     <- Adapter (yours)
   <- Driver
 <- OS 
nmap

or

nmap 
 -> OS 
   -> Driver
     -> OS
       -> Application
     <- OS
   <- Driver
 <- OS 
nmap

or

nmap 
 -> OS 
   -> Application
 <- OS 
nmap

Those other options make it much more complicated for nmap to figure out the information it wants to know, so instead of spending the time to support the 3 possible options they just block requests to yourself.

Scott Chamberlain
  • 31,164
1

Try using your IP Address instead. Localhost does not involve the entire network interface, and I would believe that nmap will work if you use your IP address instead...

See Why is there a difference between ping "localhost" and ping "local IP address"? for more details on why I believe Localhost won't work...

Community
  • 1
Benjamin Schollnick
  • 4,447