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How to Tell What Ports are Open on your own Computer
It's a good idea to regularly check what ports are open on your own
computer. If you discover a new port -- time to investigate. For example, an
open port 31337 is an almost sure sign that your computer has been taken over by
the Windows Back Orifice Trojan. (See the "How to Break into Windows 95/98
Computers" chapter for removal instructions.)
It is possible to check all your ports with just the tools that are
already part of your Windows or Unix operating system. The "netstat -a" command
will show all the ports open on your computer. Here's what I get on a home Linux
box:
~ > netstat -a
Active Internet connections
(including servers)
Proto Recv-Q Send-Q Local
Address Foreign Address State
tcp 0 134 fu.ml.org:telnet pma03.foo66.com:1030 ESTABLISHED
tcp 0 0
*:www *:* LISTEN
tcp 0 0
fu.ml.org:22 *:* LISTEN
tcp 0 0 *:smtp *:* LISTEN
tcp 0 0
*:2049 *:* LISTEN
tcp 0 0
*:660 *:* LISTEN
tcp 0 0
*:printer *:* LISTEN
tcp 0 0
*:auth *:* LISTEN
tcp 0 0
*:finger *:* LISTEN
tcp 0 0
*:imap2 *:* LISTEN
tcp 0 0
*:pop3 *:* LISTEN
tcp 0 0
*:login *:* LISTEN
tcp 0 0
*:shell *:* LISTEN
tcp 0 0
*:telnet *:* LISTEN
tcp 0 0
*:ftp *:* LISTEN
tcp 0 0
*:time *:* LISTEN
tcp 0 0 *:sunrpc *:* LISTEN
udp 0 0
*:2049 *:*
udp 0 0
*:657 *:*
udp 0 0 *:ntalk *:*
udp 0 0
*:biff *:*
udp 0 0
*:time *:*
udp 0 0 *:syslog *:*
udp 0 0 *:sunrpc *:*
raw 0 0
*:1 *:*
Active UNIX domain sockets (including
servers)
Proto RefCnt
Flags Type State I-Node Path
unix 2 [
] STREAM 3870 /dev/log
unix 2 [
] STREAM CONNECTED 3869
unix 2 [
] STREAM 475 /dev/log
unix 2 [
] STREAM CONNECTED 474
unix 2 [
] STREAM 434 /dev/log
unix 2 [
] STREAM CONNECTED 433
unix 2 [
] STREAM 281 /dev/log
unix 2 [
] STREAM CONNECTED 280
unix 2 [
] STREAM 257 /dev/log
unix 2 [
] STREAM CONNECTED 252
unix 1 [ ACC
] STREAM LISTENING 247 /dev/printer
unix 2 [
] STREAM 246 /dev/log
unix 1 [ ACC
] STREAM LISTENING 207 /dev/log
unix 2 [
] STREAM CONNECTED 198
How about seeing what ports are open on your Windows computer? If you are
not on a LAN, chances are there won't be much to see. Here's what my stand
alone Win98 computer (her name is Lovely_Lady) says when I am on America Online:
C:\WINDOWS>netstat -a
Active Connections
Proto Local
Address Foreign Address State
TCP lovely-lady:137 LOVELY_LADY:0 LISTENING
TCP lovely-lady:138 LOVELY_LADY:0 LISTENING
TCP lovely-lady:nbsession LOVELY_LADY:0 LISTENING
UDP lovely-lady:nbname *:*
UDP lovely-lady:nbdatagram *:*
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