13 Ways Through a Firewall – What You Don’t Know Will Hurt You

Proprietary Information – Copyright © 2013 by Waterfall Security Solutions Ltd. 2013
13 Ways Through A Firewall
What you don’t know will hurt you
Andrew Ginter
VP Industrial Security
Waterfall Security Solutions
andrew. ginter @ waterfall - security . com
®
Mike Firstenberg
Director of Industrial Security
michaelf @ waterfall - security . com
Scientech 2013 Symposium: Managing Fleet Assets and Performance

Firewalls
● Firewalls – separate networks and sub-
networks with different security /
connectivity needs
● Often first investment any site makes
when starting down the road to an ICS
cyber security program
● “Unified Threat Managers” – firewalls with
stateful inspection, VPNs, in-line anti-virus
scanning, intrusion detection, intrusion
prevention, anti-spam, web filtering, and
much more – but are they secure?
● DMZ – “in-between” network(s)
● ICS best practice: layers of firewalls,
layers of host and network-based defenses Photo: Red Tiger Security

Setup for Demo Scenarios
● Industrial firewall / UTM
● Business network – my laptop + “hacked host”
● Control network – ICS server to attack / take over + one other ICS
host
● Consider only one-hop compromise – into DMZ, or into ICS from DMZ

Compensating Measures
Abbrev Compensating Measure
2-FACT 2-Factor authentication
ENC Encryption
RULES Better firewall rules
HIDS Host intrusion detection / prevention system / SIEM
NIDS Network intrusion detection / prevention system / SIEM
SECUPD Security updates / patch program
UGW Unidirectional security gateway
Graphic Impact
Would have prevented / detected the attack
Would prevent / detect some variants of the attack
Would not have prevented / detected the attack

#1 Phishing / Spam / Drive-By-Download
● Single most common way through (enterprise) firewalls
● Client on business network pulls malware from internet, or activates
malware in email attachment
● “Spear-phishing” – carefully crafted email to fool even security experts
into opening attachment
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#2 Social Engineering – Steal a Password
● VPN password on sticky note on monitor, or under keyboard
● Call up administrator, weave a convincing tale of woe, and ask for the
password
● Ask the administrator to give you a VPN account
● Shoulder-surf while administrator enters firewall password
● Guess
● Install a keystroke logger
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#3 Compromise Domain Controller – Create Account
● More generally – abuse trust of external system
● Create account / change password of exposed ICS server, or firewall
itself
● Other external trust abuse – compromise external HMI, ERP, DCS
vendor with remote access, WSUS server, DNS server, etc.
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#4 Attack Exposed Servers
● Every exposed port is vulnerable:
● SQL injection
● buffer overflow
● default passwords
● hard-coded password
● denial of service / SYN-flood 2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#5 Attack ICS Clients via Compromised Servers
● Best practice: originate all cross-firewall TCP connections on ICS /
trusted side
● Once established, all TCP connections are bi-directional – attacks can
flow back to clients:
● compromised web servers
● compromised files on file servers
● buffer overflows
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#6 Session Hijacking / Man-in-the-Middle
● Requires access to communications stream between authorized
endpoints – eg: ARPSpoof (LAN), fake Wi-Fi access point, hacked DNS
server
● Insert new commands into existing communications session
● Sniff / fake session ID / cookie and re-use
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#7 Piggy-Back on VPN
● You may trust the person you have granted remote access, but should
you trust their computer?
● Broad VPN access rules – “I trust this user to connect to any machine,
on any port” makes it easy for worms and viruses to jump
● Split-tunneling allows interactive remote control
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#8 Firewall Vulnerabilities
● Firewalls are software. All large software artifacts have bugs, and
some of those bugs are security vulnerabilities and zero-days
● Vendor back-doors / hard-coded passwords
● Supply chain issues – do you trust the manufacturer? The
manufacturer’s suppliers?
● Occasional design vulnerabilities
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#9 Errors and Omissions
● Modern firewalls require 6-8 weeks full-time training to cover all
features and all configurations
● The smallest errors expose protected servers to attack
● Over time, poorly-managed firewalls increasingly resemble routers
● Well-meaning corporate IT personnel often control firewall
configurations and can reach through to “fix” ICS hosts
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#10 Forge an IP Address
● Most firewall rules are expressed in terms of IP addresses
● Any administrator can change the IP address on a laptop or
workstation
● Works only if attacker is on same LAN segment as true IP address – or
WAN routers route response traffic to a different LAN
● May need ARPSpoof to block machine with real IP
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#11 Bypass Network Security Perimeter
● Complex network architectures – path from business network to ICS
network through only routers exists, but is not obvious
● Rogue wireless access points
● Rogue cables – well meaning technicians eliminate “single point of
failure” in firewall
● ICS network extends outside of physical security perimeter
● Dial-up port
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#12 Physical Access to Firewall
● If you can touch it, you can compromise it
● Reset to factory defaults
● Log in to local serial port, change settings with CLI
● Re-arrange wiring
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

#13 Sneakernet
● Removable media, especially USB sticks, carried past physical / cyber
security perimeter
● Entire laptops, workstations and servers carried past physical / cyber
security perimeter
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

Demo
Warning: the issues demonstrated in the
following slides apply to all firewalls, not just
the firewall vendors and models illustrated. It
is a mistake to interpret the following slides
as a criticism of specific firewalls or specific
firewall vendors.

Firewall Vulnerability – Cross-Site Request Forgery

● Uses web browser credentials for logged-in sites
● “Blind” technique – script cannot read from foreign web page
● Can however, push changed data to web server, as if user had
pressed “send”
Lesson: Cross-site scripting vulnerabilities are rampant in web
applications of all kinds, including ICS applications. CSRF has been public
knowledge for over a decade
Mitigation: Modify web application to use hidden fields to echo random
data back to web site on pages that change application state. Browsers
prevent each site’s scripts from seeing data coming from another site, so
foreign scripts cannot echo random data back to protected website

Errors and Omissions – Can You See The Error?

Errors and Omissions – Address Range Too Broad

Errors and Omissions – Can You See the Error?

Errors and Omissions – Rule for DHCP Address

Errors and Omissions
● “andrews-machine” address was really for an entire subnet
● See this only when you go to the screen which defines “andrews-
machine” address
● Correcting this problem is not sufficient – the address was in the
DHCP range
● See this only when you go to the DHCP server definition screen
● Andrew’s machine needs to be given a static IP address
Lesson: Full-featured firewalls are complex. Reviewing configurations to
ensure they are safe is not straightforward.

Firewall Design Vulnerability

● Browsers enforce “can’t touch other site’s web pages” rule when
scripts and web pages come from different sites
● Within a site, scripts can touch web pages at will – this is how
complex web applications work
● Hiding many web sites behind a single proxy address is very
“convenient” – web browser is your SSL client
● Web browsers cannot enforce “can’t touch other site’s web pages”
rules when scripts and web pages all appear to originate at the
same site
Lesson: Clientless/browser SSL clients are designed to hide many sites
behind one address. Unless browser designs or clientless SSL designs
change, hosts behind such proxy-site web servers will always be
vulnerable to each other’s scripted attacks.

Hacking ICS Servers

Hacking ICS Servers – 100,000 Vulnerabilities
● A major vendor recently reported counting over 50,000 buffer-
overflow-capable C library calls in one 2,000,000 LOC product
● All such calls are currently being replaced
● Do the math:
● Assume 2% of all overflow-capable calls are vulnerabilities
● 10 major vendors world-wide, in at least 5 verticals
● Assume at least 3 2MLOC products unique to each vertical
● Assume at least 75% of these products still written in C/C++
● The math: 2% x 50,000 calls x 10 vendors x 5 verticals x 3 products x
75% = at least 100,000 vulnerabilities waiting to be found
Lesson: Attacking firewall-exposed ICS servers with zero-day exploits
will be straightforward for the foreseeable future

Keeping Score
Score Abbrev Compensating Measure
7 2-FACT 2-Factor authentication
7 ENC Encryption
11 RULES Better firewall rules
8 HIDS Host intrusion detection / prevention system / SIEM
9 NIDS Network intrusion detection / prevention system / SIEM
9 SECUPD Security updates / patch program
20 UGW Unidirectional security gateway
Graphic Score Impact
2 Would have prevented / detected the attack
1 Would prevent / detect some variants of the attack
0 Would not have prevented / detected the attack

● Headquarters in Israel, sales and operations office in the USA
● Hundreds of sites deployed in all critical infrastructure sectors
Best Practice Award 2012, Industrial Network Security
IT and OT security architects should consider Waterfall
for their operations networks
Waterfall is key player in the cyber security market –
2010, 2011, & 2012
● Strategic partnership agreements /
cooperation with: OSIsoft, GE, Siemens,
and many other major industrial vendors

Stronger Than Firewalls
● Firewalls are porous
● Given the “elephants in the room,” perimeter protection will always be
disproportionately important:
● 100,000 vulnerabilities
● Plain-text device communications
● Dissonance between ECC and IT’s “constant change”
patch programs
● Long life-cycles for physical equipment
andrew.ginter@waterfall-security.com
www.waterfall-security.com
michaelf @ waterfall - security . com
2-FACT
ENC
RULES
HIDS
NIDS
SECUPD
UGW

13 Ways Through a Firewall – What You Don’t Know Will Hurt You

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13 Ways Through a Firewall – What You Don’t Know Will Hurt You