Wednesday, April 28, 2010

traceroute scanning

something that's lots of fun to do is to scan a network with a traceroute command. what you get back is a (relatively) complete picture of the network connecting all the hosts with the specified prefix. depending on where you point it, it can be very, very big.

like i mentioned earlier, i know which node it is that stands between me and several routers that connect to different parts of the Boston internet. one of those routers goes to NOX, and another one to other residential (i think) comcast accounts. if i point the traceroute scan at a comcast node that's relatively nearby, and that contains the same IP prefix as mine (20 bits is reasonable and doesn't give back 65 thousand possible hosts), i get back a nice, complex picture of a network extending from here and across Boston, and across MA to CT, VT, and the MA-NY border.

i tried the same thing on the private 192.168 network at the institute, and got back something similar, and actually much denser (which makes sense, all hosts within the network have the same prefix, so i could get them all in one big shot, but the comcast network was relatively sparser, and seemed to have same-prefix hosts separated by nodes with different prefixes, which i don't understand...). since it's a single institution, it's organized differently - there are nodes for different users, but mainly the network divisions are more functional, with databases in one place, outgoing servers in another, administrative here, labs there. the comcast network looked much more regional, with a Hartford node, others (i get all these new englandy names confused, they all sound like Westly or Chestford or something like that).

ok, need to step back now and get more acquainted with the specifics rather than just playing with these toys...

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.

Monday, April 26, 2010


just got my first portscan result.

it's another address in boston, using skype. it's also a comcast address, and the first 16 bits are the same as my address. the prefix of the server above it says 'needham'. i guess it's strange that it's such a similar location to mine, and i suppose i could be looking into some sort of mirror that i don't understand, but i do think it's a real, other user, somewhere here in town.

nmap saw that its http ports (80 and 443) were open, and decided that they were being used by the Skype service. i can also see that port 2265 is open, the same port from which i'm receiving packets from this computer.

the other open port (2222) is associated with a website administration program, or with who knows what else.

nmap also claims with some confidence that the computer is a pocket PC running some version of windows XP.

still, i have no idea why this computer is reflecting messages through my computer. and i still haven't figured out why there's always an explicit connection through skype with another computer - other than jingping, this is the only skype connection at the moment, so it is *the other* connection. now i'll see if it shows up again...

Saturday, April 24, 2010

nmap 1

got a program called nmap, using the windows gui.

i can't really get a port scan to work on another computer. i tried to get jingping to turn off her firewall, but she said it was already off - i guess norton does its own firewall.

still, nmap has other neat functions. you can get it to do traceroute for you, along with other things, and it will hold on to all the data for you. as you do this, it creates a graphic plot of all the addresses you've been querying. if you're doing tracerouts, it plots ip paths, which is fantastic. here's what i did:

still working off the mysteries of Skype, i ran the network monitor for a few minutes, and got a list of those UDP conversations through port 34368. most of these just consist of my computer sending out a single datagram to some other address, with which i may or may not be also involved in a TCP session. a few ms later, i get a UDP back from the target. there were about 15 of these over a 5 minute period. i plugged them all into the nmap and tracerouted them (had to do this one by one, i'm going to have to get a little more sophisticated), and got back a neat plot showing how all these connections are related to me. these other IP addresses were all over the world, China, NZ, Japan, Russia, France, all over. maybe those are the supernodes, and i'm just registering with them by sending a datagram?

the plot is interesting in itself:

you can't read them but the ip address of every node along the route is listed. the maps are dynamic; you can highlight a node and all its children (those further down the route away from the center), change the center node, rotate, etc.

like i said, most of those UDP exchanges were just 2 packets, one out and one response. there were two other things that happened. one was, I sent 2 UDP packets and got back 1 RTP packet, which i think is actually a UDP packet carrying audio/video information. there wasn't anything else associated with that address, though, so i can't guess what that was about.

the other interesting thing was an instance where i sent 3 UDP packets to a certain address, with no response. i actually guessed the reason: they were being sent to jingping's laptop on campus, on the UofL wireless network, where it hasn't actually been connnected since early friday evening: i sent those UDP packets after midnight, more than 7 hours after she had disconnected.

why did this happen? one thing is, i may have left Skype running on the computer in my office, and during the day that was a connection to her laptop on the campus wireless network. or, i may have turned it off - sometimes i forget, usually i don't, but i don't usually remember if i remembered, only if i forgot (strange how that works). at any rate, for some reason, my computer, being connected with my Skype account, thought to check to see if that UofL address was still on, despite the fact that the account it had been associated with was now associated with another IP address. this doesn't make a lot of sense to me. some sort of cleanup work on Skype's part?

mysteries, mysteries.

Thursday, April 22, 2010

oh, this is neat!

i saw an ICMP 'echo request' packet! i was in an IRC channel at the time, for the first time in like 10 years, so i thought maybe it was somebody there. but the request actually had a working URL attached, which is in the title of this post ( it really was a ping, an automated, scientific ping!

internet is very, very interesting.

Tuesday, April 20, 2010


this is called portsweeping!

i saw another one, in China (Jinan, Shandong maybe), this one looking into port 6000, which can be used for remote keystroke recording.

somebody just sets up a program to search the internet for computers with vulnerable ports. it's like if someone could go and scan apartments for ones with unlocked doors or open windows - then send in the thieves! amazing!


watching the net monitor again, with network applications turned off. saw one unassociated address - tracked down to Henan, China. to look this up, i stopped the monitor and opened the web browser. then i started the monitor up again, and right away realized i had failed to check the port number.
luckily (or unluckily) i caught another one. this one was either in Georgia (.ge) or Turkey - i think the service is based in Turkey, but the address was in Georgia.

so, this address exchanged several TCP packets with my computer, none of which seemed to contain anything (i say this only because they had 'payload lengths' of zero - this is not something i have researched yet). they were exchanged through port 3389, which actually carried a label: MS WBT SERVER. what is MS WBT SERVER you ask? this is the port used by the 'Remote Desktop' utility in windows. obviously, this was something in the Caucasus searching for a computer with a somehow vulnerable port 3389.

how to tell if it's vulnerable? maybe if i was using the utility? i don't know. maybe he's watching me type right now, though i think then i'd be able to see him still. it was a total of 8 TCP packets, followed a couple of minutes later by 2 UDP packets.

very interesting!

Monday, April 19, 2010

skype port? broadcasts?

ok, very briefly because it's late.

if i leave the network monitor on for a while, it lists lots and lots of conversations between ARKIV (my computer) and other addresses out there in the world. most of these are UDP packets, but not all. of the ones that are UDP packets, i'm pretty sure that they're all associated with Skype. here is how i know:

the monitor does show when conversations are known to be controlled by a particular process like Skype. so, tonight, i record for a while, and i see two other addresses associated with Skype. one is jingping, i know, because tracert tells me that it's an insight address routed through Atlanta, and i already know that's our service in louisville. the other is somebody in new bedford MA, still in the comcast network. i don't know what that is.

anyways, so i can see jingping's IP address. it also shows up in the 'unknown' associated list of all those UDP conversations, with a different port number, 34268. all the other UDP conversations (most - i didn't look at each one) are also going to port 34268, so i deduce that they must also be associated with Skype.

so, apparently Skype is going to be an internet learning tool for me. it's very mysterious. are these other Skype users, using ARKIV as a waypoint for finding other users? i think that's what a supernode does, but from what i've read supernodes should have many, many more connections. so, i still don't know what this is all about, and skype's operations are kind of trade secrets which are hard to research online. still, i'm sure there's plenty out there for me to figure out.

okay, so there, i learned that i can identify a process by its port number. or, at least, i deduced it. it may be wrong.

Thursday, April 08, 2010


oh man. i haven't learned anything today, except that there's only so far you can take a visual simulation before it breaks. so, i've been measuring thresholds for a simulated observer at different spatial frequencies, for content within photographs which has been thresholded depending on a trial-to-trial staircase. it works pretty well for the images themselves. the original image gets compared with the image containing a thresholded band, and the observer is able to converge at a measure of the threshold over several hundred trials, similar to a human observer.

what i do is this: the original image gets filtered at the frequency in question, and the filtered image (the output of the filter) is thresholded and added back into the original image minus the filtered image. so, we actually have the original image minus the subthreshold content within the filter. if the threshold is zero, these two images are identical, i.e. they are whole, unfiltered photographs. this is the experiment as i originally ran it on myself, trying to find the just-detectable threshold (the threshold-threshold). to do the experiment simulation, the thresholded image then gets filtered again, meaning that the filter picks up the thresholded content along with residual off-frequency content. this is the only reasonable way to get the test content, since 1) that off-frequency content is there in the image and would be seen by the filter, and thus can't be ignored, and 2) the filtered band contains harmonics which wouldn't be seen by the filter.

naturally, i eventually decided to do the same experiment without the complete image; i.e., just measure threshold-thresholds for the content within the filter. i thought this would be straightforward - i just use the filtered image as the 'original', and the thresholded filtered image as the 'test'. but then, i thought, ah, almost screwed up there: the thresholded filtered image should be filtered again, just like in the original experiment. so, you can see the problem. the original content is lifted straight out of the source image, while the thresholded content gets lifted out of the source image and again out of the thresholded image, which means it will be multiplied twice by the filter. so, even if the threshold is zero, the test and original images will be different.

this is a problem. in fact, it must also be a problem in the original experiment. but, the test and original images in the original experiment are the same when the threshold is zero - i assume this is because the off-frequency content amounts to the difference between the filtered and double-filtered content, and adding the filtered content back into the image basically restores the lost content.

i need to think about this.

Monday, April 05, 2010

UDP packets

ok, so all those strange packets are UDP packets. UDP stands for User Datagram Protocol, which really means nothing to me. anyways, UDP can be used for broadcasting information across a network, and from reading a bit about it i get the impression that its generally kind of messy when compared with TCP. TCP (Transmission Control Protocol) is what is used to build a precise, static file, like a webpage or a file that you save on your computer. so, maybe what i'm seeing on my computer is just content that is broadcasted across the entire local network. still, i don't know why that is done, or why it would be done from far away places, but i'll figure it out.

promiscuous mode

was reading about 'promiscuous mode' the other night, but don't remember much about it. might explain some of the mystery traffic, but i think probably not. apparently you can tell your computer to go ahead and accept whatever traffic happens to wash over it, which i totally don't understand, and use this mode to monitor activity that isn't meant for you. but, i don't think my computer is normally promiscuous, so that may not be relevant. my laptop is probably a zombie, receiving secret orders from another zombie in bulgaria. wow! i'll figure it all out later. anyways, drove to connecticut this weekend with jingping, first time ever out of the City into the "new england". it was alright i guess.

Friday, April 02, 2010


looking at traffic again last night with the MNM, with the explicit internet applications all turned off. over something like a 20 minute period, there were conversations between my computer and maybe ten others from around the world. i checked a few of these addresses; one in bulgaria, one in italy, one in china. each was only a few packets. i didn't save the recording, which i think i'll do from now on, so maybe eventually i can figure out what these things are. is my computer a zombie? are these just scans or searches from computers in faraway places? i must know.