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Defending Your Network: Identifying and Patrolling Your True Network Perimeter Bill Cheswick Chief Scientist, Lumeta Corp Pondering and Patrolling Perimeters Bill Cheswick ches@lumeta.com http://www.lumeta.com Talk Outline Outside: mapping the Internet A discussion of perimeter defenses

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defending your network identifying and patrolling your true network perimeter

Defending Your Network: Identifying and Patrolling Your True Network Perimeter

Bill Cheswick

Chief Scientist, Lumeta Corp

pondering and patrolling perimeters

Pondering and Patrolling Perimeters

Bill Cheswick

ches@lumeta.com

http://www.lumeta.com

talk outline
Talk Outline
  • Outside: mapping the Internet
  • A discussion of perimeter defenses
  • Strong host security
  • Mapping and understanding intranets
  • The past and future of Microsoft host security:
    • my Dad’s computer
the internet mapping project

The Internet Mapping Project

An experiment in exploring network connectivity

motivations
Highlands “day after” scenario

Panix DOS attacks

a way to trace anonymous packets back!

Visualization experiments

Curiosity about size and growth of the Internet

Databases for graph theorists, grad students, etc.

Motivations
methods data collection
Methods - data collection

Single reliable host connected at the company perimeter

Daily full scan of Lucent

Daily partial scan of Internet, monthly full scan

One line of text per network scanned

Unix tools

Use a light touch, so we don’t bother Internet denizens

methods network discovery nd
Methods - network discovery (ND)

Obtain master network list

network lists from Merit, RIPE, APNIC, etc.

BGP data or routing data from customers

hand-assembled list of Yugoslavia/Bosnia

Run a traceroute-style scan towards each network

Stop on error, completion, no data

Keep the natives happy

intranet implications of internet mapping
Intranet implications of Internet mapping
  • High speed technique, able to handle the largest networks
  • Light touch: “what are you going to do to my intranet?”
  • Acquire and maintain databases of Internet network assignments and usage
related work
Related Work
  • See Martin Dodge’s cyber geography page
  • MIDS - John Quarterman
  • CAIDA - kc claffy
  • Mercator
  • “Measuring ISP topologies with rocketfuel” - 2002
    • Spring, Mahajan, Wetherall
  • Enter “internet map” in your search engine
ttl probes
TTL probes

Used by traceroute and other tools

Probes toward each target network with increasing TTL

Probes are ICMP, UDP, TCP to port 80, 25, 139, etc.

Some people block UDP, others ICMP

advantages
Advantages
  • We don’t need access (I.e. SNMP) to the routers
  • It’s very fast
  • Standard Internet tool: it doesn’t break things
  • Insignificant load on the routers
  • Not likely to show up on IDS reports
  • We can probe with many packet types
limitations
Limitations
  • View is from scanning host only
    • Multiple scan sources gives a better view
  • Outgoing paths only
  • Level 3 (IP) only
    • ATM networks appear as a single node
  • Not all routers respond
    • Some are silent
    • Others are “shy” (RFC 1123 compliant), limited to one response per second
data collection complaints
Data collection complaints

Australian parliament was the first to complain

List of whiners (25 nets)

On the Internet, these complaints are mostly a thing of the past

Internet background radiation predominates

intranet uses of don t scan list
Intranet uses of Don’t Scan list
  • Hands off particular business partners
  • Hands off especially sensitive networks
    • Hanging ATMs
    • 3B2s with broadcast storms
    • Wollongong software (!) on factory floor computers
  • Intranet vs. ISP customer networks
visualization goals
Visualization goals

make a map

show interesting features

debug our database and collection methods

hard to fold up

geography doesn’t matter

use colors to show further meaning

visualization of the layout algorithm

Visualization of the layout algorithm

Laying out the Internet graph

a simplified map for the internet layouts
A simplified map, for the Internet layouts
  • Minimum distance spanning tree uses 80% of the data
  • Much easier visualization
  • Most of the links still valid
  • Redundancy is in the middle
slide22

Colored by

AS number

map coloring
Map Coloring

distance from test host

IP address

shows communities

Geographical (by TLD)

ISPs

future

timing, firewalls, LSRR blocks

slide27

Colored by distance

from scanning host

slide28

US military

reached by ICMP ping

slide29

US military networks

reached by UDP

yugoslavia

Yugoslavia

An unclassified peek at a new battlefield

slide38

Perimeter defenses are a traditional means of protecting an area without hardening each of the things in that area

why use a perimeter defense
Why use a perimeter defense?
  • It is cheaper
    • A man’s home is his castle, but most people can’t afford the moat
  • You can concentrate your equipment and your expertise in a few areas
  • It is simpler, and simpler security is usually better
    • Easier to understand and audit
    • Easier to spot broken parts
what s wrong with perimeter defenses
What’s wrong with perimeter defenses
  • They are useless against insider attacks
edinburgh castle
fell through a hole in its perimeter

fell to siege in three years in 16th century

ran out of food and water

Unsuccessful attack by Bonnie Prince Charlie in 1745

Devastated in 1544 by the Earl of Hertford

Edinburgh Castle
what s wrong with perimeter defenses53
What’s wrong with perimeter defenses
  • They are useless against insider attacks
  • They provide a false sense of security
    • You still need to toughen up the inside, at least some
    • You need to hire enough defenders
what s wrong with perimeter defenses56
What’s wrong with perimeter defenses
  • They are useless against insider attacks
  • They provide a false sense of security
    • You still need to toughen up the inside, at least some
  • They don’t scale well
slide57

The Pretty Good

Wall of China

i can but you probably can t
I can, but you probably can’t
  • “Skinny-dipping” on the Internet since the mid 1990s
  • The exposure focuses one clearly on the threats and proactive security
  • It’s very convenient, for the services I dare to use
  • Many important network services are difficult to harden
skinny dipping rules
Skinny dipping rules
  • Only minimal services are offered to the general public
    • Ssh
    • Web server (jailed Apache)
    • DNS (self chrooted)
    • SMTP (postfix, not sendmail)
  • Children (like employees) and MSFT clients are untrustworthy
  • Offer hardened local services at home, like SAMBA (chroot), POP3 (chroot)
  • I’d like to offer other services, but they are hard to secure
skinny dipping requires strong host security
Skinny dipping requires strong host security
  • FreeBSD and Linux machines
  • I am told that one can lock down an MSFT host, but there are hundreds of steps, and I don’t know how to do it.
  • This isn’t just about operating systems: the most popular client applications are, in theory, very dangerous and, in practice, very dangerous.
    • Web browsers and mail readers have many dangerous features
lately i have been cheating
Lately, I have been cheating
  • Backup hosts are unreachable from the Internet (which is a perimeter defense of sorts), and do not trust the exposed hosts
  • Public servers have lower privilege than my crown jewels
  • This means I can experiment a bit more with the exposed hosts
skinny dipping flaws
Skinny dipping flaws
  • Less depth to the defense
skinny dipping flaws68
Skinny dipping flaws
  • Less defense in depth
  • No protection from denial-of-service attacks
hopes for microsoft client security
Hopes for Microsoft client security?
  • I’ll talk about it at the end of the talk.
intranets

Intranets

Networked perimeter defenses

intranets have been out of control since they were invented
Intranets have been out of control since they were invented
  • This is not the fault of network administrators
    • The technology is amenable to abuse
    • Decentralization was a design goal of the Internet
  • CIO and CSOs want centralized control of their network
  • The legacy information is lost with rapid employee turnover
  • M&A breaks carefully-planned networking
perimeter security gives a false sense of security
Perimeter security gives a false sense of security
  • “Crunchy outside, and a soft, chewy center”
    • Me
  • I think 40 hosts is about the most that I can control within a perimeter.
    • Others can probably do better
  • Internet worms are pop quizzes on perimeter security
history of the project and lumeta
History of the Project and Lumeta
  • Started in August 1998 at Bell Labs
  • April-June 1999: Yugoslavia mapping
  • July 2000: first customer intranet scanned
  • Sept. 2000: spun off Lumeta from Lucent/Bell Labs
  • June 2002: “B” round funding completed
  • 2003: sales >$4MM
  • After three years of a service offering, we built IPSonar so you can run it yourself.
slide81

This was

Supposed

To be a

VPN

leaks
Leaks
  • We call the leaks shown in the maps “routing leaks”
  • Can we find hosts that don’t forward packets, but straddle the perimeter?
  • Yes: we call them “host leaks”, and detecting them is Lumeta’s “special sauce”
how to find host leaks
How to find host leaks
  • Run a census with ICMP and/or UDP packets
  • Test each machine to see if it can receive a probe from one network, and reply on another
  • Not just dual-homed hosts
  • DMZ hosts, business partner machines, misconfigured VPN access
leak detection
A sends packet to B, with spoofed return address of D

If B can, it will reply to D with a response, possibly through a different interface

Leak Detection

mitt

Mapping host

D

A

Internet

intranet

C

B

Test host

leak detection88
Packet must be crafted so the response won’t be permitted through the firewall

A variety of packet types and responses are used

Either inside or outside address may be discovered

Packet is labeled so we know where it came from

Leak Detection

mitt

Mapping host

D

A

Internet

intranet

C

B

Test host

leaks are not always bad
Leaks are not always bad
  • Depends on the network policy
  • Often, outgoing leaks are ok
  • Sometimes our test packets get through, but not the services you are worrying about
  • “Please don’t call them leaks”
  • Until this test, there was no way for the CIO to detect them, good or bad
  • Patent pending…
we developed lot of stuff
We developed lot of stuff
  • Leak detection (that’s the special sauce)
  • Route discovery
  • Host enumeration and identification
  • Server discovery
  • Lots of reports…the hardest part
  • Wireless base station discovery
  • And more…ask the sales people
  • The “zeroth step in network intelligence”
    • me
some lumeta lessons
Some Lumeta lessons
  • Reporting is the really hard part
    • Converting data to information
  • “Tell me how we compare to other clients”
  • Offering a service was good practice, for a while
  • We have >70 Fortune-200 companies and government agencies as clients
  • Need-to-have vs. want-to-have
microsoft client security

Microsoft client security

It has been getting worse

case study my dad s computer
Case study:My Dad’s computer
  • Windows XP, plenty of horsepower, two screens
  • Applications:
    • Email (Outlook)
    • “Bridge:” a fancy stock market monitoring system
    • AIM
  • Cable access, dynamic IP address, no NAT, no firewall, outdated virus software, no spyware checker
this computer was a software toxic waste dump
This computer was a software toxic waste dump
  • It was burning a quart of software every 300 miles
  • The popups seemed darned distracting to me
  • But he thought it was fine
    • Got his work done
    • Didn’t want a system administrator to break his user interface somehow
microsoft s augean stables
Microsoft’s Augean Stables
  • 3000 oxen, 30 years, that’s roughly one oxen-day per line of code in Windows
windows me
Windows ME

Active Connections - Win ME

Proto Local Address Foreign Address State

TCP 127.0.0.1:1032 0.0.0.0:0 LISTENING

TCP 223.223.223.10:139 0.0.0.0:0 LISTENING

UDP 0.0.0.0:1025 *:*

UDP 0.0.0.0:1026 *:*

UDP 0.0.0.0:31337 *:*

UDP 0.0.0.0:162 *:*

UDP 223.223.223.10:137 *:*

UDP 223.223.223.10:138 *:*

windows 2000
Windows 2000

Proto Local Address Foreign Address State

TCP 0.0.0.0:135 0.0.0.0:0 LISTENING

TCP 0.0.0.0:445 0.0.0.0:0 LISTENING

TCP 0.0.0.0:1029 0.0.0.0:0 LISTENING

TCP 0.0.0.0:1036 0.0.0.0:0 LISTENING

TCP 0.0.0.0:1078 0.0.0.0:0 LISTENING

TCP 0.0.0.0:1080 0.0.0.0:0 LISTENING

TCP 0.0.0.0:1086 0.0.0.0:0 LISTENING

TCP 0.0.0.0:6515 0.0.0.0:0 LISTENING

TCP 127.0.0.1:139 0.0.0.0:0 LISTENING

UDP 0.0.0.0:445 *:*

UDP 0.0.0.0:1038 *:*

UDP 0.0.0.0:6514 *:*

UDP 0.0.0.0:6515 *:*

UDP 127.0.0.1:1108 *:*

UDP 223.223.223.96:500 *:*

UDP 223.223.223.96:4500 *:*

windows xp this laptop
Windows XP, this laptop

Proto Local Address Foreign Address State

TCP ches-pc:epmap ches-pc:0 LISTENING

TCP ches-pc:microsoft-ds ches-pc:0 LISTENING

TCP ches-pc:1025 ches-pc:0 LISTENING

TCP ches-pc:1036 ches-pc:0 LISTENING

TCP ches-pc:3115 ches-pc:0 LISTENING

TCP ches-pc:3118 ches-pc:0 LISTENING

TCP ches-pc:3470 ches-pc:0 LISTENING

TCP ches-pc:3477 ches-pc:0 LISTENING

TCP ches-pc:5000 ches-pc:0 LISTENING

TCP ches-pc:6515 ches-pc:0 LISTENING

TCP ches-pc:netbios-ssn ches-pc:0 LISTENING

TCP ches-pc:3001 ches-pc:0 LISTENING

TCP ches-pc:3002 ches-pc:0 LISTENING

TCP ches-pc:3003 ches-pc:0 LISTENING

TCP ches-pc:5180 ches-pc:0 LISTENING

UDP ches-pc:microsoft-ds *:*

UDP ches-pc:isakmp *:*

UDP ches-pc:1027 *:*

UDP ches-pc:3008 *:*

UDP ches-pc:3473 *:*

UDP ches-pc:6514 *:*

UDP ches-pc:6515 *:*

UDP ches-pc:netbios-ns *:*

UDP ches-pc:netbios-dgm *:*

UDP ches-pc:1900 *:*

UDP ches-pc:ntp *:*

UDP ches-pc:1900 *:*

UDP ches-pc:3471 *:*

freebsd partition this laptop
FreeBSD partition, this laptop

Active Internet connections (including servers)

Proto Recv-Q Send-Q Local Address Foreign Address (state)

tcp4 0 0 *.22 *.* LISTEN

tcp6 0 0 *.22 *.* LISTEN

microsoft really means it about improving their security
Microsoft really means it about improving their security
  • Their security commitment appears to be real
  • It is a huge job
  • Opposing forces are unclear to me
  • It’s been a long time coming, and frustrating
microsoft really means it about improving their security102
Microsoft really means it about improving their security
  • They need world-class sandboxes, many more layers in their security, and much safer defaults
  • A Microsoft “terminal” will benefit millions of users
windows ok
Windows OK
  • Thin client implemented with Windows
  • It would be fine for maybe half the Windows users
    • Students, consumers, many corporate and government users
  • It would be reasonable to skinny dip with this client
    • Without firewall or virus checking software
windows ok104
Windows OK
  • No network listeners
    • None of those services are needed, except admin access for centrally-administered hosts
  • Default security settings, all available on the control panel security screen
  • Security settings can be locked
windows ok105
Windows OK
  • Reduce privileges in servers and all programs
  • Sandbox programs
    • Belt and suspenders
windows ok cont
Windows OK (cont)
  • There should be nothing you can click on, in email or a web page, that can hurt your computer
    • No portable programs are executed ever, except…
  • ActiveX from approved parties
    • MSFT and one or two others. List is lockable
office ok
Office OK
  • No macros in Word or PowerPoint. No executable code in PowerPoint files
  • The only macros allowed in Excel perform arithmetic. They cannot create files, etc.
vulnerabilities in ok
Vulnerabilities in OK
  • Buffer overflows in processing of data (not from the network)
  • Stop adding new features and focus on bug fixes
  • Programmers can clean up bugs, if they don’t have a moving target
    • It converges, to some extent
defending your network identifying and patrolling your true network perimeter109

Defending Your Network: Identifying and Patrolling Your True Network Perimeter

Bill Cheswick

Chief Scientist, Lumeta Corp