ee579t/12 #1 spring 2003 © 2000-2003, richard a. stanley ee579t / cs525t network security 12:...

Spring 2003© 2000-2003, Richard A. Stanley

EE579T/12 #1

EE579T / CS525TNetwork Security

12: Intrusion Detection Systems;Wireless Security

Prof. Richard A. Stanley


EE579T/12 #2

Overview of Tonight’s Class

• Schedule projects

• Review last week’s lesson

• Another MS Windows problem

• Virus checkers and food for thought

• Intrusion detection systems

• Wireless security


EE579T/12 #3

Project Scheduling

• We will NOT meet on 15 April

• First projects: 8 April

• Final projects: 22 April

• Let’s have volunteers for each evening, keeping in mind your work schedules


EE579T/12 #4

Summary of last time...

• Computer crime is a fast-growing area of illegal activity

• “That’s where the money is”• Computers and networks are regulated by a

large and growing body of law• Both civil and criminal issues involved• Liability is a major consideration for any

business or practitioner


EE579T/12 #5

Another Windows Problem

• “Remote attacker could gain total control of a machine running Windows 2000”

• “Unchecked buffer in a Windows 2000 component used to handle the World Wide Web Distributed Authoring and Versioning (WebDAV) protocol could allow an attacker to cause a buffer overflow on a machine running IIS”

• “Attackers could mount a denial-of-service attack against such machines or execute their own malicious code in the security context of the IIS service, gaining unfettered access to the vulnerable system”

Source: Computerworld, March 17, 2003


EE579T/12 #6

Virus Checkers

• Three major vendors worldwide – (2 US, 1 Finland)

• Many more malicious code exploits in the zoo than in the wild (~200X)– Who are the zookeepers?– What does it take to get a zoo specimen out?

• Who are the software writers?• What are the implications?


EE579T/12 #7

Intrusion Detection Systems

• Oddly enough, these are systems designed to detect intrusions into protected systems

• Security intrusion (per RFC 2828):– A security event, or a combination of multiple

security events, that constitutes a security incident in which an intruder gains, or attempts to gain, access to a system (or system resource) without having authorization to do so.


EE579T/12 #8

What’s a Security Incident?

• A security event that involves a security violation. (See: CERT, GRIP, security event, security intrusion, security violation.)

• In other words, a security-relevant system event in which the system's security policy is disobeyed or otherwise breached.

• "Any adverse event which compromises some aspect of computer or network security." [R2350]

Source: RFC 2828, page 152; emphasis added


EE579T/12 #9

Why Do We Need This?

• With the exception of authentication systems, most of the defenses we have studied up to now are directed towards intruders coming from outside the firewall

• These systems are not perfect--some intruders will get through

• Moreover, defenses such as firewalls cannot protect against intruders on the inside


EE579T/12 #10

Intrusion Detection Functions

• Monitor protected networks and computers in real time (or as close to real time as is practicable)

• Detect security incidents– Requires a policy, and a way for the IDS to know

what that policy is

• Respond– Raise an alarm– Send some automated response to the attacker


EE579T/12 #11

IDS vs. Auditing

• Audits tend to be a posteriori– But an IDS can be seen as performing a

constant, near real time audit function

• To perform an audit, you need to know what the policy is– Audit measures departures from the policy

norms– Audits depend on system logs


EE579T/12 #12

Early IDS’s

• Emulated the audit function– Crawled the logs, looking for deviations from

policy-permitted actions– Intent was to speed up the audit, making it

nearly real time– Still a useful approach

• IDS technology has been around only since the early 1990’s; not too mature


EE579T/12 #13

IDS Uses

• Monitor system usage– Determine access, usage patterns– Plan for capacity engineering

• Monitor specific problem areas

• Serve as a deterrent– Sort of like the “burglar alarm” label on a

house, even if there is really no alarm


EE579T/12 #14

Log Files

• Are evidence if an intrusion occurs– Must be stored in their original, unmodified

form, otherwise inadmissible in court– Provide data from which trends can be deduced– Can be subjected to forensic analysis– Probably needed to assess level of system

compromise/damage and to restore to state prior to intrusion


EE579T/12 #15

Legal Issues - 1

• Privacy of your employees– Courts have held that employees have little

expectation of privacy in the workplace, especially if told so at the outset

• email can be monitored at work by employer

• phone calls can be monitored at work by employer

• doing either of these things outside the workplace violates the wiretap statutes (18 USC § 2516, etc.)


EE579T/12 #16

Legal Issues - 2

• What if the IDS discovers illegal acts being performed on/by your network?– Employees using the network for illegal

activities– Outsiders having planted zombie programs so

that your system attacks others– What is your responsibility and liability?


EE579T/12 #17

Legal Issues - 3

• This may be a Catch-22 issue– If an attacker is using your system, law

enforcement may want you to continue to allow that to happen so they can apprehend the attacker

• If you interrupt the attack, could be interpreted as obstruction of justice

– But, if you allow the attack to continue, you may be liable for damages to those attacked

• Get legal advice--beforehand!


EE579T/12 #18

What About Automated Response?

• Tempting capability

• If attacking your system is illegal, what makes your attack on the attacker less illegal?

• What if you are, or are acting on behalf of, a governmental entity and the attacker is also a governmental entity?– Casus belli


EE579T/12 #19

IDS Architecture

Sensor Sensor Sensor

Sensor

Sensor

ManagementConsole


EE579T/12 #20

Console

• Monitors and controls sensors– Sets policy, alarm levels, etc.– Stores logs

• Must have secure communications with sensors– Encrypted connection– Out of band (OOB)


EE579T/12 #21

IDS Types

• Network-based (NIDS)– Monitors the network backbone

• Network node-based (NNIDS)– Monitors network nodes, not the backbone

• Host-based (HIDS)– This is the “log crawler” that started it all

• Gateway (GIDS)– NIDS in series with the network


EE579T/12 #22

What Can It See?

• Network packets

• OS API calls

• System logs

• How do we merge this data to detect intrusions?


EE579T/12 #23

Host-Based

• Sits on a host as a background task

• Monitors (potentially)– traffic to and from the host– OS API calls– system logs

• Adds to processing load on the host, so host must be able to support the extra load


EE579T/12 #24

Network-based

• NIDS sensors placed on network backbone– Can view only packet traffic passing by, much

like a classic passive sniffer– Does not place processing load on network, but

the NIDS platform must be capable of dealing with network traffic speeds

• Software can usually handle 100 Mbps

• Hardware only 2-3 times faster

• If network is faster, looks only at subset of packets


EE579T/12 #25

Network Node-based

• Used to inspect intrusions directly into network nodes– Effectively a blending of HIDS and NIDS– Used to protect mission-critical machines– Again, a background process on existing nodes,

so node must be able to handle added processing load


EE579T/12 #26

Gateway

• In series with network– Often set to block prohibited traffic

automatically– Think of it as an in-network firewall with an

extended rule set– Must be able to keep up with network load


EE579T/12 #27

Deployment

• Putting in an IDS is a complex and time-consuming affair– Typically, start simple and add functionality as

you learn more about the network– NIDS tends to see more and load network least– Follow up with HIDS on selected hosts,

perhaps NNIDS on critical nodes

• Policy has to be in place first


EE579T/12 #28

Attack Signatures

• Critical to success of any IDS• Must be maintained, just like virus signatures

– You want some visibility into this– Do you want strangers deciding what is an attack

on your critical systems?

• Some IDS’s let you write/modify signatures, others do not

• CVE: http://www.cve.mitre.org/


EE579T/12 #29

IDS Deployment

• First, design the IDS sensor and management layout

• Next, deploy the IDS – Test the network for normal operation– Test the IDS

• Run packaged attacks to see if all are detected

• Document performance and repeat test regularly

– Tune the IDS


EE579T/12 #30

Sampling of IDS Products• RealSecure: http://www.iss

.net/products_services/enterprise_protection/rsnetwork/sensor.php

• NFR: http://www.nfr.net/

• Snort: http://www.snort.org/

• SnortSnarf: http://www.silicondefense.com/software/snortsnarf/


EE579T/12 #31

IDS Summary

• IDS’s can be useful in monitoring networks for intrusions and policy violations

• Up-to-date attack signatures and policy implementations essential

• Many types of IDS available, at least one as freeware

• Serious potential legal implications• Automated responses to be avoided


EE579T/12 #32

Wireless Network Security

• Wireless networks growing at a rapid pace– Gartner Group predicts wireless installations

will multiply >7X by 2007 to over 31M

• Business drivers– Installation cost and time– Mobility– Flexibility– Operating costs


EE579T/12 #33

Wireless Inherently Insecure

• Wired networks contain (or try) signals to a wired path, which must be physically tapped to compromise line security– Possible to physically discover the tap

• Wireless networks deliberately broadcast data into space, where it can be intercepted by anyone with proper receiver– Data tap impossible to discover


EE579T/12 #34

This Isn’t New News

• Since early days, wireless vendors strove to provide privacy equivalent to that available on the wired network– WEP = wired equivalent privacy– This is not a high standard to meet

• They succeeded, but that wasn’t good enough for user requirements


EE579T/12 #35

Projects

• We have several project teams that will report on wireless security issues, so I will not go into great detail here

• A few things to whet your appetites– How does a wireless network work?– How can you “join up?”– What about the encryption?


EE579T/12 #36

How It Works

• Clients send probes

• Access points broadcast beacons and, often, their Server Set ID (SSID)

• When a client finds an access point with an acceptable signal level and a matching SSID, a connection is established

• Many networks are built precisely to facilitate connection by “foreign” users


EE579T/12 #37

NetStumbler


EE579T/12 #38

Other Interesting Things

• Wardriving: http://www.wardriving.com/

• Warchalking: http://www.warchalking.org/

• Airsnort: http://airsnort.shmoo.com/

What other little“gifts” await us?


EE579T/12 #39

Wireless Security Summary• It’s a problem, owing to the nature of

wireless transmission

• So far, security implementations have left a lot to be desired

• Project presentations will provide added details

• Growth is explosive, both in legitimate and illegitimate wireless activity

ee579t/12 #1 spring 2003 © 2000-2003, richard a. stanley ee579t / cs525t network security 12:...

Documents

security incident

security violation

stanley slide

security context

systems security policy

securityrelevant system

stanley summary

stanley whats