FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2nd ed.

4Finding Network Vulnerabilities

By Whitman, Mattord, & Austin © 2008 Course Technology

Learning Objectives

Name the common categories of vulnerabilities Discuss common system and network

vulnerabilities Locate and access sources of information about

emerging vulnerabilities Identify the names and functions of the widely

available scanning and analysis tools

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 2

Introduction

To maintain secure networks, information security professionals must be prepared to identify system vulnerabilities, whether by hiring system assessment experts or by conducting self-assessments using scanning and penetration tools

Network security vulnerability is defect in product, process, or procedure that, if exploited, may result in violation of security policy, which in turn might lead to loss of revenue, loss of information, or loss of value to the organization

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 3

Common Vulnerabilities

Common vulnerabilities fall into two broad classes:

Defects in software or firmware Weaknesses in processes and procedures

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 4

Defects in Software or Firmware

Buffer overruns (or buffer overflows) arise when quantity of input data exceeds size of available data area (buffer)

Injection attacks can occur when programmer does not properly validate user input and allows an attacker to include input that, when passed to a database, can give rise to SQL injection vulnerabilities

Network traffic is vulnerable to eavesdropping because a network medium is essentially an open channel

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 5

Defects in Software or Firmware (continued)

How can security professionals remain abreast of all the vulnerabilities?

First and perhaps foremost, they must know:– Organization’s security policies– Software and hardware the organization uses

Information security professionals should regularly consult these public disclosure lists:– Vendor announcements – Full disclosure mailing lists – CVE: the common vulnerabilities and exposures

databaseFirewalls & Network Security, 2nd ed. - Chapter 4 Slide 6

Vendor Announcements

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BugTraq

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Weaknesses in Processes and Procedures

Just as hazardous as software vulnerabilities More difficult to detect and fix because they

typically involve the human element Often arise when policy is violated or processes

and procedures that implement policy are inadequate or fail

To ensure security policy is implemented, organizations should hold regular security awareness training and regularly review policies and their implementation

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 9

Scanning and Analysis Tools

To truly assess risk within computing environment, technical controls must be deployed using strategy of defense in depth

Scanners and analysis tools can find vulnerabilities in systems, holes in security components, and unsecured aspects of the network

Scanners, sniffers, and other such vulnerability analysis tools are invaluable because they enable administrators to see what attackers see

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 10

Scanning and Analysis Tools (continued) Scanning tools are typically used as part of an

attack protocol Attack protocol is a series of steps or processes

used by attacker, in logical sequence, to launch attack against target system or network

This may begin with a collection of publicly available information about a potential target, a process known as footprinting

Attacker uses public Internet data sources to perform searches to identify network addresses of the organization

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 11

Footprinting

Most important information for footprinting purposes is IP address range

Another piece of useful information is name, phone number, and e-mail address of the technical contact

This research is augmented by browsing the organization’s Web pages since Web pages usually contain information about internal systems, individuals developing Web pages, and other tidbits, which can be used for social engineering attacks

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 12

Footprinting (continued)

To assist in footprint intelligence collection process, an enhanced Web scanner can be used that, among other things, can scan entire Web sites for valuable pieces of information, such as server names and e-mail addresses

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 13

Sam Spade

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 14

Fingerprinting

Next phase of attack protocol is data-gathering process called fingerprinting, a systematic survey of all of the target organization’s Internet addresses that is conducted to identify network services offered by hosts in that range

Fingerprinting reveals useful information about internal structure and operational nature of the target system or network

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 15

Port Scanners

Port scanning utilities (port scanners) are tools used by both attackers and defenders to identify computers that are active on a network, as well as ports and services active on those computers, functions and roles the machines are fulfilling, and other useful information

The more specific the scanner is, the better and more useful the information it provides is, but a generic, broad-based scanner can help locate and identify rogue nodes on the network

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 16

Port Scanners (continued)

Port is a network channel or connection point in a data communications system

Within TCP/IP, TCP and UDP port numbers differentiate multiple communication channels used to connect to network services being offered on same device

In all, there are 65,536 port numbers in use for TCP and another 65,536 port numbers for UDP

Ports greater than 1023 typically referred to as ephemeral ports and may be randomly allocated to server and client processes

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 17

Port Scanners (continued)

Why secure open ports? Open port is an open door and can be used by

attacker to send commands to a computer, potentially gain access to a server, and possibly exert control over a networking device

The general policy statement is to remove from service or secure any port not absolutely necessary to conducting business

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 18

Firewall Analysis Tools

Understanding exactly where organization’s firewall is located and what existing rule sets do are very important steps for any security administrator

Several tools that automate remote discovery of firewall rules and assist administrator (or attacker) in analyzing rules to determine exactly what they allow and what they reject

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 19

Firewall Analysis Tools (continued)

Administrators wary of using same tools attackers use should remember:– Regardless of the nature of the tool used to

validate or analyze firewall’s configuration, it is the intent of the user that dictates how information gathered will be used

– To defend a computer or network, it is necessary to understand ways it can be attacked; thus, a tool that can help close up an open or poorly configured firewall helps network defender minimize risk from attack

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 20

Operating System Detection Tools

Identifying target computer’s operating system is very valuable to attacker

Once the operating system is known, it is easy to determine all vulnerabilities to which it might be susceptible

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 21

Vulnerability Scanners

Passive vulnerability scanner listens in on the network and identifies vulnerable versions of both server and client software

Active vulnerability scanners scan networks for highly detailed information by initiating network traffic in order to identify security holes– These scanners identify exposed usernames and

groups, show open network shares, and expose configuration problems and other vulnerabilities in servers

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 22

Vulnerability Scanners (continued)

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Vulnerability Validation

Often, an organization requires proof that system is actually vulnerable to certain attacks

May require such proof to avoid having system administrators attempt to repair systems that are not broken or because they have not yet built satisfactory relationship with vulnerability assessment team

Class of scanners exists that exploit remote machine and allow vulnerability analyst (penetration tester) to create accounts, modify Web pages, or view data

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Vulnerability Validation (continued)

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Packet Sniffers

Network tool that collects copies of packets from network and analyzes them

Sometimes called a network protocol analyzer Can provide network administrator with valuable

information for diagnosing and resolving networking issues

In the wrong hands, sniffer can be used to eavesdrop on network traffic

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 26

Packet Sniffers (continued)

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Wireless Security Tools

Wireless connection, while convenient, has many potential security holes

Security professional must assess risk of wireless networks

Wireless security toolkit should include ability to sniff wireless traffic, scan wireless hosts, and assess level of privacy or confidentiality afforded on wireless network

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 28

Wireless Security Tools (continued)

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Penetration Testing

Penetration test involves using all techniques and tools available to attacker in order to attempt to compromise or penetrate an organization’s defenses

Penetration testing can be performed by internal group (so called “red teams”) or outsourced to external organization

A variable of the penetration test, whether performed internally or outsourced, is amount of information provided to the red team

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 30

Penetration Testing (continued)

Three categories of testing:– Black box: red team is given no information

whatsoever about the organization and approaches the organization as external attacker

– Gray box: red team is given some general information about the organization such as general structure, network address ranges, software and versions

– White box: red team has full information on the organization and its structure

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 31

Chapter Summary

To maintain secure networks, information security professionals must be prepared to systematically identify system vulnerabilities

Often done by performing self-assessment using scanning and penetration tools testing

Common vulnerabilities fall into two classes:– Defects in software or firmware

– Weaknesses in processes and procedures

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 32

Chapter Summary (continued)

Information security professionals should regularly consult vendor announcements, full disclosure mailing lists, and the common vulnerabilities and exposures (CVE) database

To assess risk within a computing environment, network professionals must use tools such as intrusion detection systems (IDPS), active vulnerability scanners, passive vulnerability scanners, automated log analyzers, and protocol analyzers (sniffers)

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 33

Chapter Summary (continued)

Many organizations use penetration test to assess their security posture on a regular basis

Penetration test team (red team) uses all techniques and tools available to attackers in order to attempt to compromise or penetrate an organization’s defenses

Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 34