The Pseudo-Internal Intruder: A New Access Oriented Intruder Category

Master’s Thesis Presentation

Brownell K. CombsMay 7, 1999

OutlineWhy are we concerned with intruders and

what can we do about them?How does categorizing intruders help

intrusion detection research?What is the Pseudo-Internal Intruder?What can the Pseudo-Internal Intruder do?How can we defend against it?How do these defenses work?

The Problem of IntrusionsCSI/FBI 1999 Computer Crime and

Security Survey (4th Annual Report) Approx. $124,000,000 in Financial Losses Only 1% Claimed No Security Incident

CERT statistics show 67% increase in incidents handled annually from ‘94 to ‘98

Intrusion Detection SystemsMany think that it may never be possible to

create ‘completely secure’ systemsIDS is the next best thing Owners of systems want one or more of the

following: recognize presence of an intruder prevent them from doing harm make similar future intrusion more difficult attempt to catch the intruder

IDS ResearchStudying Intruders (techniques, habits,

etc) is an important area of IDS researchResearchers in the field and IDS builders

in industry must have some scheme with which to categorize intruders

These schemes serve as a basic framework for discussing and thinking about the issue of Intrusion Detection

Intruder Categories 2 main approaches to placing intruders

into different categoriesIntruder oriented: focus on the

intruder’s access to the system Anderson’s classic external/internal scheme

Attack oriented: focus on the attack the intruder executes Neumann’s modes of compromise scheme

What scheme do we need?Least amount of category ambiguity for

IDS Designers and SysAdmins This best provided by narrowly defined

categories that are distinct from one another Example: How useful is it to have an

‘external intruder’ category that refers to both Internet Hackers and janitors inside the building?

DefinitionsPhysical Configuration - all of the hardware

used in a distributed system included the location of each item

Network Configuration - how all of those hardware items are connected and how they interact with each other

Net/Phy Perimeter - separation between a distributed system’s net/phy configuration and the rest of the world.

Sample Physical Configuration

SampleNetwork Configuration

Pseudo-Internal IntruderA new distinct category for the access

oriented intruder categorization scheme

P-I Intruder is an intruder without the privileges of an authorized user and who has circumvented the perimeter defenses of a system to attack the system via its internal network (network configuration)

Box Diagram of Access Oriented Categories

3 kinds of P-I IntrudersInsiders with physical access (desktop

connection, wiring closets, server rooms)Outsiders with same physical access as

above (gained through subterfuge or force)

Outsiders with special data access (personal modems that circumvent perimeter defense)

Tools and Techniques 1) Network Assessment Tools

Active and Passive2) Packet Sniffers

Hardware and Software3) Exploits

Steps executed in a certain order4) Denial of Service Attacks

Network Saturation and Traffic Misdirection

Example Scenario #1: Industrial Espionage Agent#1 gains employment with custodial

services and has access to wiring closetsConnects a hardware sniffer to the

network for several daysRemoves the sniffer and finds it captured

sensitive communications between senior company executives

Mission Accomplished

Example Scenario #2: Disgruntled Employee#2 is a basic network user with access to

multiple desktop connectionRuns a network assesment tool and software

sniffer off of a shared machineFinds multiple vulnerabilities and an account

and password of a SysAdminLogs in as SysAdmin (becomes an Internal

Intruder) and deletes databases.Mission Accomplished

Defending Against the Pseudo-Internal IntruderThree phases:

Deny intruders access to the system Mitigate the consequences of intruders

gaining access to the system Detect, Monitor, and Record any intrusions

Since Pseudo-Internal Intruders require access to the internal network, we will focus on it when examining these steps

Preventing Intruder AccessPhysical Perimeter Security: stop as many

potential intruders as possible from gaining physical access to the system (Guards, Gates, Locked Doors, etc.)

Physical configuration control: ensuring that unauthorized hardware is not introduced to the system and authorized hardware is not used for unauthorized actions (TEMPEST, Conduit, Metal Cases)

Mitigating Intruder AccessIf an intruder cannot read information or

write (affect a change) to the system then the danger of an intruder is diminished

Network configuration control: managing the aspects of the network configuration to ensure the highest degree of security Encrypt Communications, Switched-Intelligent

hubs and routers, smaller segments, etc.

Detecting Intruder AccessNetwork configuration monitoring:

continuously observing all aspects of the network configuration searching for evidence of intruders

If an intruder does gain access to the system the most effective response will be a human one. Successful monitoring and reporting allows a quick response from SysAdmins

Case Study - Two PhasesExecute a set of Pseudo-Internal Intruder

attacks against a testbed system with state of practice security measures CSI/FBI ‘99 Survey showed only 42 out of 501

respondents used any intrusion detectionExecute the same set of attacks against

the testbed system after implementing the security recommendations of the thesis

Case Study - The Attacks 1)Packet Sniffer – Software [Laptop] 2)Network Assessment Tool – Active [Rogue

Outside Connect] 3)Exploit – Ping of Death [Laptop] 4)Exploit (Hacker Program) – WinNuke (Ping of

Death) [Laptop] 5)Denial of Service Attack – Ping Flood [Laptop] 6)Denial of Service Attack – Smurf Attack

[Rogue Outside Connect]

Case Study Phase 1 - Network Configuration

Case Study - Changes made for Phase 2Network divided into 2 segmentsAll Mission Crit. Communication

EncryptedNetwork Intrusion Detection Monitoring

Device placed in Mission Crit. SegmentNetwork scanned for unknown IP and

MAC addressesRMON monitoring utilities used

Case Study Phase 2 - Network Configuration

Case Study - The ResultsSecurity Changes addressed the

vulnerabilities discovered in phase 1 No access control for devices using network No network traffic control mechanisms No internal network monitoring for intruders

Network Configuration Monitoring and Network Configuration Control decrease the danger of a P-I Intruder to systems

ConclusionsThe Pseudo-Internal Intruder Category

addresses an area of system security that did not exist prior to the proliferation of distributed systems

The category provides a platform on which to understand and define the capabilities of this new type of intruder, thereby facilitating the detection and defense against such intruders

Access Oriented: AndersonExternal: unauthorized users attacking a

system through external data connections

Internal: Legitimate: authorized for part of system Masqueraders: unauthorized users logged in

as legitimate users Clandestine: users logged in that have the

power to turn off some audit logs

Attack Oriented: NeumannCompromise from outside: come from

above or laterally at same abstraction layer (security and logic flaws)

Compromises from within: obtained with privileges of the given layer

Compromises from below: come from a lower layer of abstraction (OS, hardware based attacks)