HackTrick

A domain name server provides information on the names and numbers
assigned to computers on the Internet. For example, dns1.wurld.net and
dns2.wurld.net contain information on happyhacker.org, techbroker.com,
securitynewsportal.com, thirdpig.com and sage-inc.com. When you query
dns1.wurld.net about other computers, it might have to go hunting for that
information from other name servers. That's why you might get a timed out
failure.
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Once you know the domain servers for an online service, set one of them for the
server for your nslookup program. Here's how you do it:

C:\ >nslookup
Default Server: DNS1.wurld.net
Address: 206.61.52.11

Now give the command:

> server 207.217.126.41
Default Server: ns1.earthlink.net
Address: 207.217.126.41

Next command should be:
> set q=mx
> earthlink.net
Server: ns1.earthlink.net
Address: 207.217.126.41

earthlink.net MX preference = 5, mail exchanger = mx04.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx06.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx00.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx01.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx02.earthlink.net
earthlink.net MX preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net nameserver = ns3.earthlink.net
earthlink.net nameserver = ns1.earthlink.net
earthlink.net nameserver = ns2.earthlink.net
mx00.earthlink.net internet address = 207.217.120.28
mx01.earthlink.net internet address = 207.217.120.29
mx02.earthlink.net internet address = 207.217.120.79
mx03.earthlink.net internet address = 207.217.120.78
mx04.earthlink.net internet address = 207.217.120.249
mx05.earthlink.net internet address = 207.217.120.31
mx06.earthlink.net internet address = 207.217.120.23
ns1.earthlink.net internet address = 207.217.126.41
ns2.earthlink.net internet address = 207.217.77.42
ns3.earthlink.net internet address = 207.217.120.43
>

Your own online service will usually not mind and may even be glad if you use
telnet to read your email. Sometimes a malicious person or faulty email program
will send you a message that is so screwed up that your email program can't
download it. With telnet you can manually delete the bad email. Otherwise tech
support has to do it for you.

If you think about it, this ability to forge email is a huge temptation to
spammers. How can your online provider keep the bad guys from filling up a
victim's email box with garbage? The first time a bad guy tries this, probably
nothing will stop him or her. The second time the online provider might block
the bad guy at the firewall, maybe call the bad guy's online provider and kick
him or her and maybe get the bad guy busted or sued.

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You can go to jail warning: Sending hundreds or thousands of junk emails to bomb
someone's email account is a felony in the US.

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You can get sued warning: Spamming, where you send only one email to each
person, but send thousands or millions of emails, is borderline legal. However,
spammers have been successfully sued when they forge the email addresses of
innocent people as senders of their spam.
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Now that you know how to read and write email with telnet, you definitely have
something you can use to show off with. Happy hacking!

Oh, here's one last goodie for advanced users. Get netcat for Windows. It's a
free program written by Weld Pond and Hobbit, and available from many sites, for
example
http://www.atstake.com/research/tools/#network_utilities . It is basically
telnet on steroids. For example, using netcat, you can set up a port on your
Windows computer to allow people to telnet into a DOS shell by using this
command:

C:\>nc -L -p 5000 -t -e cmd.exe

You can specify a different port number than 5000. Just make sure it doesn't
conflict with another port by checking with the netstat command. Then you and
your friends, enemies and random losers can either telnet in or netcat in with
the command:

C:\>nc -v [ipaddress of target] [port]

Of course you will probably get hacked for setting up this port. However, if you
set up a sniffer to keep track of the action, you can turn this scary back door
into a fascinating honeypot. For example, you could run it on port 23 and watch
all the hackers who attack with telnet hoping to log in. With some programming
you could even fake a unix-like login sequence and play some tricks on your
attackers.