Application-layer firewalling: Raise your

perimeter IQ

Joel SnyderOpus One

Acknowledgements

• Products from Check Point, Cyberguard, NetScreen, Nortel Networks, Symantec, Secure Computing, Watchguard

• Support from Andy Briney, Neil Roiter at Information Security

http://infosecuritymag.techtarget.com/

Firewalls have been around for a very long time

“[AT&T’s gateway creates] a sort of crunchy shell around a soft, chewy center.” (Bill Cheswick, Design of a Secure Internet Gateway, April, 1990)

1989 1991 1993 1995 1997 1999 2001 2003 2005

First firewalls deployed in Internet-connected organizations

“Firewalls and Internet Security” published

TIS toolkit commonly available

Cisco buys PIX (Network Translation)

CheckPoint revenues cross $100m

WatchGuard introduces 1st FW appliance

Surely firewall makers have been busy since

1999 ?Clear market

trends• Faster• Cheaper• Smaller

New Guard: NetScreen (Juniper), Watchguard, SonicWALL

Old Guard: Cisco, Check Point

Clear product trends

• Add VPN features Site-to-site Remote Access (?)

• Add policy-based URL control Websense-type

• Add interfaces No longer just

inside, outside, DMZ

Shirley firewall makers have been busy since

1999 ?Clear market

trends• Faster• Cheaper• Smaller

New Guard: NetScreen (Juniper), Watchguard, SonicWALL

Old Guard: Cisco, Check Point

Clear product trends

• Add VPN features Site-to-site Remote Access (?)

• Add policy-based URL control Websense-type

• Add interfaces No longer just

inside, outside, DMZ

Incremental improvements are not very exciting

• Smaller, cheaper, faster: that’s great• VPNs, more interfaces: that’s great

• But what have you done for me lately?

• To answer that, we need to digress to the oldest battle in all of firewall-dom: proxy versus packet filter!

Arguments between Proxy and Stateful PF continued

Proxy• More secure

because you can look at application data stream

• More secure because you have independent TCP stacks

Stateful PF• Faster to write• Faster to adapt• Faster to run• Faster also means

cheaper

Proxy-based firewalls aren’t dead… just slow!

Proxy

Packet Filtering

Src=10.1.1.99Dst=5.6.7.8

TCP/IP

Src=1.2.3.4Dst=5.6.7.8

Kernel

Inside network = 10.1.1.0/24

Outside net = 1.2.3.4

RTL

Process Space

Firewall Landscape: five years ago

• IBM eNetwork• Secure Computing• Altavista Firewall• TIS Gauntlet• Raptor Eagle• Elron• Cyberguard• Ukiah Software

• NetGuard• WatchGuard• SonicWALL• Check Point• Livermore Software• Milkyway• Borderware• Global Internet

Stateful Packet Filtering dominates the market

Stateful Packet Filtering

IP

Kernel

Check PointCisco NetScreen SonicWALL

Freeware-based products: Ipchains, IPF, Iptables, IPFW

FW Newcomers:Fortinet, Toshiba, Ingate, Enterasys, many others

But… the core argument was never disputed

• Proxy-based firewalls do have the possibility to give you more control because they maintain application-layer state information

• The reality is that proxy-based firewalls rarely went very far down that path Why? Market demand, obviously…

Firewall Evolution:What we hoped for…

• Additional granular controls on a wide variety of applications

• Intrusion detection and prevention functionality

• Vastly improved centralized management systems

• More flexible deployment options

Firewall Evolution:What we found…

• Additional granular controls on somea wide variety of applications

• Limited intrusion detection and prevention functionality

• Vastly improved centralized management systems

• More flexible deployment options

Why? Market demand, obviously…

Additional Granular Controls focused on a few

applications• Everybody loves

HTTP management Header filtering File type & MIME

type blocking Embedded Data

blocking (Javascript) Virus scanning, URL

Filtering

• Other applications are piecemeal FTP SMTP

VoIP File Sharing

HTTP-oriented featuresserved “pressure points”

HTTP Action Controls

Filename & MIME type blocking

Header Filtering

SOAP controls

URL Translation

Can Block within HTTP…

Virus detection

URL filtering/ blocking

CyberGuardPost/Put/ Delete

Filename; no MIME blocking Full Basic Yes

ActiveX, Java, Javascript, VBScript, XML

Yes, external server WebSense

Netscreen None

Filename .EXE & .ZIP; no MIME blocking No No No ActiveX, Java

Yes, internal or external server

WebSense plus local URL list

WatchGuard Post MIME blocking Limited Set No NoActiveX, Java, Cookies None WebBlocker

SecureComputingAll

Filename & MIME type blocking Full Block/Allow No

ActiveX, Java, Javascript, VBScript

Local scanning, 2 types (signature/heuristic)

Smartfilter and local URL list

SymantecCan block 'upload' only

Filename blocking by extension No No No

WebDAV, DCOM

Local scanning

Rating system and local URL list

Check PointGet/Post/ Put/Head

Filename by wildcard; no MIME blocking Full Basic Yes

ActiveX, Java, Javascript, Vbscript

Yes, external server

OPSEC and local URL list

Advanced Controlsare diverse across

products

Product FTP H.323 HTTP LDAP NNTP RealAudioSIP SMTP POP DNS IMAP Socks SNMP CIFSCyberGuard • • • • • • • •Netscreen • • • • • •WatchGuard • • •Secure Computing• • • • • • •Symantec • • • • • • •Check Point • • • • • •

•Differentiating between “advanced” controls and “basic” controls was easy to do.

•Proxy-based firewalls proved to be almost undistinguishable from their “insecure” stateful packet filtering brethren.

•Vendors appear to be reactive, not proactive.

Virus Scans and Policy Controls are simple, right?

• No! Some firewalls insisted on having virus and/or URL scanning happen “off box”

• No! Some firewalls can’t configure where you scan for viruses

• No! Some devices don’t have virus scanning

• No! Some firewalls don’t support a local list of blocked URLs

Conclusion: it’s not simple

We’ve learned how to write good GUIs, haven’t we?

• Not in the firewall business, we haven’t

• Additional granularity means additional thinking about resources

• Products are … disappointing

The firewall people have a lot to

learn from the SSL VPN people

Centralized management has improved a bit

• Folks who had it are doing slightly better than they were

• Folks who didn’t have it now generally have something

We’re still missing a general policy management system for firewalls

Many of the centralized management tools have very rough edges

“Intrusion” is the new buzzword in security

Rate-based IPS technology

• In firewalls, means “SYN flood protection”

• May be smart (NS)• May include

shunning (SecComp, WG, CP)

Content-based IPS technology

• Based on IDS-style thinking

• May have small signature base (NS, CP)

• May be an “IDS with the IPS bit on” (Symantec)

So what’s going on in the firewall business?

• Products are diverging, not converging• Personalities of products are distinct• IPS is a step forward, but not

challenging the world of standalone products

• Rate of change of established products is slow compared to new entries

What does this mean for me and my firewall?

• Products are diverging

• Personalities are distinct

• IPS weaker than standalone

• Change rate slow

• Matching firewall to policy is hard; change in application or policy may mean changing product!

• Aggressive adoption of new features unlikely in popular products; need new blood to overcome product inertia

Application-layer firewalling

Joel SnyderOpus One

Member, Information SecurityMagazine test alliance

jms@opus1.com

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