chapter 9 security. the threat environment 3 figure 9-1: csi/fbi survey companies face many attacks...

Chapter 9

Security

The Threat Environment

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Figure 9-1: CSI/FBI Survey

• Companies Face Many Attacks– Viruses (and other malware)

– Insider abuse of net access

– Laptop theft

– Unauthorized access by insiders

– Denial-of-service attacks

– System penetration

– Sabotage

– Theft of proprietary information

– Fraud

– Telecoms eavesdropping and active wiretaps

In Order ofDecreasing Frequency

There are manytypes of attacks

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Figure 9-1: CSI/FBI Survey

• Very Common Successful Incidents

– Viruses and other malware

– Insider abuse of net access

– Laptop theft

• Low-Frequency / High-Damage Attacks

– Theft of proprietary information ($2.7 M per incident)

– Denial-of-service attacks ($1.4 M per incident)

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Figure 9-2: Malware

• Malware

– A general name for evil software

• Viruses

– Pieces of code that attach to other programs

– When infected programs execute, the virus executes

– Infect other programs on the computer

– Spread to other computers by e-mail attachments, IM, peer-to-peer file transfers, etc.

– Antivirus programs are needed to scan arriving files• Also scans for other malware

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Figure 9-2: Malware

• Worms

– Stand-alone programs that do not need to attach to other programs

– Can propagate like viruses through e-mail, etc.• But this require human gullibility, which is slow

– In addition, vulnerability-enabled worms jump to victim hosts directly

• Can do this because hosts have vulnerabilities

• Vulnerability-enabled worms can spread with amazing speed

• Vendors develop patches for vulnerabilities but companies often fail or are slow to apply them

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Figure 9-2: Malware

• Payloads

– After propagation, viruses and worms execute their payloads (damage code)

– Payloads erase hard disks, send users to pornography sites if they mistype URLs

– Trojan horses are exploitation programs that disguise themselves as system files

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Figure 9-2: Malware

• Attacks on Individuals

– Social engineering is tricking the victim into doing something against his or her interests

– Spam is unsolicited commercial e-mail

– Credit card number theft is performed by carders

– Identity theft is collecting enough data to impersonate the victim in large financial transactions

– Fraud involves get-rich-quick schemes, medical scams

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Figure 9-2: Malware

• Attacks on Individuals

– Adware pops up advertisements

– Spyware collects sensitive data and sends it to an attacker

– Phishing: sophisticated social engineering attack in which an authentic-looking e-mail or website entices the user to enter his or her username, password, or other sensitive information

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Figure 9-3: Human Break-Ins (Hacking)

• Human Break-Ins

– Viruses and worms rely on one main attack method

– Humans can keep trying different approaches until they succeed

• Hacking

– Hacking is breaking into a computer

– Hacking is intentionally using a computer resource without authorization or in excess of authorization

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• Scanning Phase

– Send attack probes to map the network and identify possible victim hosts

– Nmap programming is a popular program for scanning attacks (Figure 9-4)

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Figure 9-4: Nmap

IP Range to Scan

Type of Scan

Identified Host and

Open Ports

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• The Term “Exploit” is Used in Different Ways

– Noun: The actual break-in

– Noun: Exploit is the program used to make the break-in

– Verb: Attackers exploit the computer

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• After the Break-In, the Hacker

– Becomes invisible by deleting log files

– Creates a backdoor (way to get back into the computer)

• Backdoor account—account with a known password and super user privileges

• Backdoor program—program to allow reentry; usually Trojanized

• Rootkit—stealthy backdoor that cannot be detected by the operating system

– Does damage at leisure

New

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Figure 9-5: Distributed Flooding Denial-of-Service Attack

Victim60.168.47.47

Attacker1.34.150.37

Handler

Handler

Zombie

Zombie

Zombie

AttackCommand Attack Packet

Attack Packet

Attack Packet

AttackCommand

AttackCommand Attack

Command

AttackCommand

The attacker installs handler and zombie programs on victimsThe attacker sends an attack command to handlers.

Handlers send attack commands to zombies.The zombies overwhelm the victim with attack packets.

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Figure 9-6: Bots

BotBotSoftware

Update

Command

Human Master

Bots are like zombies,but they can be updated

by the human masterto give new functionality.

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Figure 9-7: Types of Attackers

• Traditional Attackers:

– Traditional Hackers

• Hackers break into computers

• Driven by curiosity, a feeling of power, and peer reputation

– Virus writers

• Vandals

• Amoral

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– Script kiddies use scripts written by experienced hackers and virus writers

• Have limited knowledge and abilities

• But the large numbers of script kiddies makes them very dangerous collectively

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– Disgruntled employees andex-employees

• Dangerous becausethey have knowledge ofand access to systems

• Too often ignored, they can do extensive damage

• The most dangerous employee attackers are IT and security staff members

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• Criminal Attackers

– Most attacks are now made by criminals rather than amateurs

– Crime generates funds that criminal attackers need to increase attack sophistication

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• On the Horizon

– Cyberterror: Attacks by terrorists

– Cyberwar: Attacks by nations

– Potential for massive attacks

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Figure 9-8: Planning Principles

• Security Is a Management Issue, Not a Technical Issue

– Without good management, technology cannot be effective

• Comprehensive Security

– An attacker only has to find one weakness

– A firm needs comprehensive security to close all avenues of attack

– This requires centralized security planning and management

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Figure 9-8: Planning Principles

• Defense in Depth

– Every protection breaks down sometimes

– Attacker should have to break through several lines of defense to succeed

– Providing this protection is called defense in depth

Countermeasure2

Stops the Attack

Countermeasure1

(fails)

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Figure 9-9: Access Control

• Enumerating and Prioritizing Assets

– Firms must enumerate and prioritize the assets they have to protect

– Otherwise, security planning is impossible

• Risk Analysis

– Must balance threat risks against the cost of protection

– Don’t overpay for security

– Don’t fail to protect sensitive assets

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Figure 9-9: Access Control

• Companies Must Then Develop an Access Control Plan for Each Asset

– The plan includes the AAA protections

– Authentication is proving the identity of the person wishing access

– Authorization is determining what the person may do if they are authenticated

– Auditing is logging data on user actions for later appraisal. May send an alarm if certain conditions are found.

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Figure 9-10: Authentication

Verifier

Applicant

Verifier

Applicant

1.Credentials

(Password, etc.)2. OK?

3. OK andAuthorizations

4. Welcome

AuthenticationServer

The applicant is the person who wishes to prove his or her identity.The verifier is the person who wants to authenticate the applicant.

The applicant sends credentials (passwords, etc.).Usually a central authentication server judges the credentials.

This provides consistency in authentication.

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Figure 9-11: Password Authentication

• Passwords– Strings of characters

– Typed to authenticate someone wanting to use a username (account) on a computer

• Benefits– Ease of use for users (familiar)

– Inexpensive because built in to operating systems


• Problems

– Passwords that are common words or names are widespread

• Can be cracked quickly with dictionary attack

– Variations of common words (capitalizing the first character, adding a digit at the end, etc.), can be broken almost as quickly by hybrid dictionary attack that looks for these tricks

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• Passwords should be complex

– Mix case (A and a), digits (6), and other keyboard characters ($, #, etc.)

– Can only be cracked with brute force attacks (trying all possibilities)

• Passwords should be long

– Eight characters minimum

– Each added character increases the brute force search time by a factor of about 70

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• Other Concerns

– If people are forced to use long and complex passwords, they tend to write them down

– People should use different passwords for different sites

• Otherwise, compromising a password will give access to multiple sites.

• But many people use the same password at multiple sites

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• Critique each of the following passwords, tell what attack can break it, and tell how difficult it will be for the attack to guess the password.

– swordfish

– Processing1

– SeAtTLe

– R7%t&

– 4h*6tU9$^l

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Figure 9-12: Digital Certificate Authentication

• Public and Private Keys

– Each party will have both a public key and a private key

– Each party makes its public key available to everybody

– Each party keeps its private key secret

• Digital Certificate

– Tamper-proof file that gives anamed party’s public key

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Calculation Digital Certificate

Authentication

Public key ofthe person

the applicantclaims to be

Applicantdoes a calculation

with his or herPrivate key

Verifier tests the calculation with the public key of theclaimed party. If the test succeeds, the applicant mustknow the secret private key of the claimed party, which

only the claimed party should know.

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• Appraisal

– Digital signature authentication gives extremely strong authentication

– Very expensive: must set up infrastructure for distributing public-private key pairs

– The firm must do the labor of creating, distributing, and installing private keys.

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Figure 9-13: Biometric Authentication

• Biometric Authentication

– Authentication based on bodily measurements

– Promises to eliminate passwords

• Fingerprint Scanning

– Dominates biometrics use today

– Simple and inexpensive

– Substantial error rate (misidentification)

– Often can be fooled fairly easily by determined impostors

– Not a problem for low-risk situations like home computers

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• Iris Scanners

– Scan the iris (colored part of the eye)with a camera (not a laser beam)

– Irises are complex, so very strong authentication

– Expensive

• Face Recognition

– Camera allows analysis of facial structure

– Can be done surreptitiously—without the knowledge or consent of person being scanned

– Very high error rate and easy to deceive

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• Error Rates and Deception

– Error rates (the frequency of identification errors when there is no deception) typically are higher than vendors claim

• Vendors test under idealized conditions

– Deception (deliberately trying to fool the system) is easier than vendors claim

• Especially for fingerprint recognition

– The in-the-field accuracy of biometrics is uncertain

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Figure 9-14: Firewall Operation

InternalCorporateNetwork

Attacker

AttackPacket

InternetFirewall

HardenedClient PC

AllowedLegitimate Packet

Hardened Server Internet

DeniedAttackPacket

Log File LegitimateHost

LegitimatePacket

Ingress Filtering

Egress Filtering

Firewalls inspect each packet.Legitimate packets are allowed through.

Provable attack packets are dropped and logged.

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Figure 9-15: Stateful Firewall Filtering

• Stateful Firewall Filtering

– There are several types of firewall filtering

– Stateful inspection is the dominant methodology today

– Stateful firewalls often use other filtering mechanisms as secondary mechanisms

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• Connection Initiation Attempts– Some Packets Attempt to Open a Connection

– Example: packets with TCP segments whose SYN bits are set

– Stateful firewalls have default rules for connection-opening attempts

Site

StatefulBorderFirewall

ExternallyInitiated

Connections areRejected

By Default

Internally Initiated ConnectionsAre Allowed by default

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• Stateful Inspection Access Control Lists (ACLs)

– ACLs modify the default behavior for ingress or egress

– Ingress ACL rules: allow access to selected internal servers

– Egress ACL rules: prevent access to certain external servers

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• Packets that Do Not Attempt to Open a Connection

– Most packets do not attempt to open a connection

– Very simple behavior

• If the packet is part of an established connection, it is passed without further inspection. (However, these packets can be filtered if desired)

• If the packet is not part of an established connection, it is dropped and logged

– This simplicity makes the cost of processing most packets minimal

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Stateful Firewalls: Recap

All Packets

Connection-OpeningAttempts

Other Packets

Default Behavior

ACL Exceptions

Part ofPreviouslyPermitted

Connection

Not Part ofPreviouslyPermitted

Connection

Drop PacketAccept Packet

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• Perspective

– Stateful firewalls’ simple operation leads to inexpensive stateful firewall operation

– However, stateful inspection firewall operation is highly secure

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Figure 9-17: Ingress Access Control List (ACL) for a Stateful Inspection Firewall

• 1. If packet’s source and destination sockets are in the connection table, PASS.

– If the packet is part of an previously established connection, pass it without further filtering.

• 2. If the packet’s source and destination sockets are not in the connection table and the packet is not a connection-opening attempt, DROP and LOG.

– Drop any packet that is not a connection-opening attempt and that is not part of an established connection.

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• 3. If protocol = TCP AND destination port number = 25, PASS and add connection to connection table.

– This rule permits external access to all internal mail servers.

• 4. If IP address = 10.47.122.79 AND protocol = TCP AND destination port number = 80, PASS and add connection to connection table.

– This rule permits access to a particular webserver (10.47.122.79)

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• 5. Deny All AND LOG

– If earlier rules do not result in a pass or deny decision, this last rule enforces the default rule of banning all externally initiated connection-opening attempts.

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Figure 9-18: Firewalls, Intrusion Detection Systems (IDSs), and Intrusion Prevention Systems (IPSs)

• Firewalls– Drop provable attack packets

• Intrusion Detection Systems (IDSs)– Very sophisticated filtering—better than firewalls

– Identify suspicious packets

– Do not drop--suspicious packets may be legitimate

• Intrusion Prevention Systems (IPSs)– Use IDS filtering mechanisms

– Drop suspicious packets highly likely to be attacks

– Ignore other suspicious packets

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Figure 9-18: Firewalls, Intrusion Detection Systems, and Intrusion Prevention Systems

• IDS and IPS filtering

– Stream Analysis

• Analyze streams of packets to identify suspicious patterns

– Deep packet inspection

• Inspect headers and messages at the internet, transport, and application layers

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Figure 9-18: Firewalls, Intrusion Detection Systems, and Intrusion Prevention Systems

Firewalls IDSs IPSs

Processing Power Required

Modest Heavy Heavy

Maturity Fairly Mature Still immature. Too many false positives

Tuning reduces false positives but is labor-intensive

New.

Only used to stop attacks that can be identified fairly accurately.

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Figure 9-19: Cryptographic Systems

• Cryptographic Systems

– Provide security to multi-message dialogues

• At the Beginning of Each Communication Session

– The two parties usually mutually authenticate each other

Party A Party B

Initial Authentication

A’s CredentialsTo B

B’s CredentialsTo A

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• Message-by-Message Protection

– After this initial authentication, cryptographic systems provide protection to every message

– Encrypt each message for confidentiality so that eavesdroppers cannot read it

Party A Party BMessages Encrypted for Confidentiality

EavesdropperCannot Read Messages

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• Message-by-Message Protection

– Adds an electronic signature to each message

• The electronic signature authenticates the sender

• It also provides message integrity: receiver can tell if a message has been changed in transit

Party A Party BElectronic Signature

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Figure 9-20: Symmetric and Public Key Encryption

Symmetric Key Encryption for Confidentiality

Message“Hello”

Cipher &Key

SymmetricKey

Party A

Party B

Network

Encrypted Message

Encryption uses anon-secret cipher

(encryption method )and a secret key

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Encrypted Message

SymmetricKey

Party A

Party B

InterceptorNetwork

Interceptor cannot readencrypted messages en route

Encrypted Message

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Encrypted Message Message“Hello”

Cipher &Key

SymmetricKey

SameSymmetric

KeyParty A

Party B

InterceptorNetwork

Receiver decrypts the messageusing the same cipher

and the same symmetric key

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Public Key Encryption for Confidentiality

EncryptedMessage

EncryptedMessage

Party A Party B

Encrypt withParty B’s Public Key

Decrypt withParty B’s Private Key

Decrypt withParty A’s Private Key

Encrypt withParty A’s Public Key

Note:Four keys are used to encryptand decrypt in both directions

Figure 9-21: Other Aspects of Protection

• Symmetric Key Dominates Encryption for Confidentiality

– Accounts for 99% of all encryption for confidentiality

– Dominates because it is computationally simple and therefore inexpensive

• Public Key Encryption for Confidentiality is Only Used Rarely and for Very Short Messages

– Computationally, 100 to 1,000 times slower than symmetric key encryption

– However, public key encryption for authentication is more common

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• Hardening Servers and Client PCs

– Some attack packets inevitably reach hosts

– Hardening is setting up computers to protect themselves

– Server Hardening

• Back up so that restoration is possible

• Patch security vulnerabilities

• Use host firewalls

• …

Attacks

Host

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• Hardening Servers and Client PCs

– Client PC Hardening

• As with servers, patching vulnerabilities, having a firewall, and implementing backup

• Also, a good antivirus program that is updated regularly

• Client PC users often make errors or sabotage hardening techniques

• In corporations, group policy objects (GPOs) can be used to centrally manage security on Windows clients

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• Vulnerability Testing

– Protections are difficult to set up correctly

– Vulnerability testing is attacking your system yourself or through a consultant

– There must be follow-up to fix vulnerabilities that are discovered

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Figure 9-22: Incident Response

• Even with the best security, successful attacks sometimes happen

1. Detect the Attack

2. Stop the Attack

3. Repair the Damage

4. Punish the Attacker

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• Major Attacks and CSIRTs

– Major Incidents

– Must be handled by the computer security incident response team (CSIRT)

• Must include members of senior management, the firm’s security staff, members of the IT staff, members of functional departments, and the firm’s public relations and legal departments

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• Disasters and Disaster Recovery

– Natural and humanly made disasters

– Need a disaster recovery plan ahead of time

– Need a backup site and procedures to shift work there

– Need rehearsals to iron out difficulties and develop speed

chapter 9 security. the threat environment 3 figure 9-1: csi/fbi survey companies face many attacks...

Documents

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malware malware

malware attacks

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scanning attacks figure

attacks viruses

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malware payloads