probe for open ports from within a firewalled network?

soviet/funk

Is there a tool or method I can use to probe which ports are open in a firewall?

I'm in a temp job as a teacher and between classes need to do changes to my websites via ftp & ssh, but the network here doesn't seem to allow anything but web browsing. They have very good reasons to do so, I'm sure... but I need to get around this without having to contact the IT dept and wait for a week before they say no. (Or even yes, but by then i won't be here anymore)

FTP (PASV & active) and SSH are not working. I have one ssh server running on a nonstandard port, but can't connect to that either. I have a java applet that streams on port 3000, and can't get a proper connection there either.

So what I'm thinking is that there could be a tool or method which probes the firewall and finds out which ports i can use for these connections, so i can set up an intermediate machine for necessary sshing and ftping. Anyone that can give me a quick pointer?

Of course an entire protocol may be blocked, in which case i'm fuckered, but it's worth a try. Spares me some night work.

thanks
kevin
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psycepa · Veteran Joined: 27 Dec 2004 Posts: 1637 Location: Poland

maby you can try app called nmap ?
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bo czytac, to trzeba ze zrozumieniem (c) by psycepa
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"Life is complex. It has its real and imaginary part."

soviet/funk · Posted: Mon Oct 31, 2005 9:53 am Post subject:

oh yeah! I've even tried nmap before on an other network (found out which computer on a network was hogging all traffic).
Do i just probe the network gateway IP? Currently emerging, at least wget works...

kevin
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soviet/funk · Posted: Mon Oct 31, 2005 10:15 am Post subject:

Not much happy yet. The final responding hop of a traceroute attempting to find the server i need to connect to seems to be a cisco router with only telnet (23/tcp) and http (80/tcp) open. Does this mean anything? What does this router do with other traffic? Does it really block all other port traffic?
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psycepa · Veteran Joined: 27 Dec 2004 Posts: 1637 Location: Poland

telnet seems strange, at least for me, as it is considered as deprecated and ssh is used instead...
_________________
RLUNo. 376073
bo czytac, to trzeba ze zrozumieniem (c) by psycepa
"nigdy nie kloc sie z glupcem, najpierw sprowadzi cie do swojego poziomu a potem pokona doswiadczeniem"
"Life is complex. It has its real and imaginary part."

soviet/funk · Posted: Wed Nov 09, 2005 5:44 pm Post subject:

well, i wouldn't use telnet for anything either, not ftp either. Not on my own servers, anyway.
But many routers/adsl modems have a telnet interface for configuring. If you call a help line at your ISP, they'll often telnet to your cisco router to check and set your config. http config is usually disabled on these, although still there as an option. So i guess that's what the open port was there for.

Thanks for listening. I'm no longer in that temp job, but nmap will surely be handy next time i find myself in a network "prison".

kevin
_________________
Vitals:
Precision M65
AMD64/3500+/SATA/nForce3/GT6600
a whole shitload of gentoo servers