Tuesday, April 27, 2010

network scanning

okay, so i know how to use CIDR notation now. knowing this, i can get a network scan to work; you specify a prefix, and look for hosts on that network. last night i did this for a while on a couple of targets (jingping's insightbb network, and an AOL network around Cincinnati that i found through another connected skype user), and found that i could recognize a computer using skype by the ports it had open - all hosts i had looked at which i knew were running skype had open TCP ports on 80 and 443. so, when i saw a couple of hosts with those open ports, i guessed it must be skype, and confirmed it with more intensive, specific scans.

i also looked at my own network. given what i know, i was the only visible skype user. there was another machine which nmap guessed was a VOIP router, which is kind of interesting.

so, looking at networks is interesting. you can see all the hosts at once, get quick summaries of just what type of host they might be and what they're doing, and all of this with a couple of simple tools and some ability to recognize states (which the tools are of course better than me at doing).

also, from my office, i can see that my home network is linked by a single router to a different node than i see from home, one of the NOX comcast nodes (i can't remember what it is from home, but it isn't NOX, which is what ties together all these new england university networks). so, that router has access to several dozen hosts including my computer, and also to several higher comcast nodes, through which it can send traffic off in various directions. in other words, i think that that router is the single bottleneck for traffic from my home computer - i'm one hop from the open internet.

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