Desktop Security

After completing this lesson, you should be able to do the following:

•Describe the different types of software and hardware attacks

•List types of desktop defences

•Explain how to recover from an attack

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Attacks on Desktop Computers

• Most attacks fall into two categories– Malicious software attacks – Attacks on hardware

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Malicious Software Attacks

• Malware – Wide variety of damaging or annoying attack

software– Enters a computer system without the owner’s

knowledge or consent

• Primary objectives of malware– Infect a computer system with destructive software – Conceal a malicious action

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Infecting Malware

• Viruses – Malicious program that needs a ‘‘carrier’’ to survive– Two carriers

• Program or document

• User

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Infecting Malware (cont’d.)

• Viruses have performed the following functions:– Caused a computer to crash repeatedly– Erased files from a hard drive– Installed hidden programs, such as stolen software,

which is then secretly distributed from the computer– Made multiple copies of itself and consumed all of

the free space in a hard drive– Reduced security settings and allowed intruders to

remotely access the computer– Reformatted the hard disk drive

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Infecting Malware (cont’d.)

• Types of computer viruses– File infector– Resident– Boot– Companion– Macro– Polymorphic

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Infecting Malware (cont’d.)

• Worms– Take advantage of a vulnerability in an application or

an operating system – Enter a system– Deposit its payload– Immediately searches for another computer that has

the same vulnerabiliy

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Infecting Malware (cont’d.)

• Different from a virus– Does not require program or user

• Actions that worms have performed include – Deleting files on the computer – Allowing the computer to be remote-controlled by an

attacker

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Concealing Malware

• Trojan horse (or just Trojan) – Program advertised as performing one activity but

actually does something else– Typically executable programs that contain hidden

code that attacks the computer system

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Concealing Malware (cont’d.)

• Rootkit – Set of software tools – Used to break into a computer, obtain special

privileges to perform unauthorized functions– Goal is not to damage a computer directly– Go to great lengths to ensure that they are not

detected and removed– Replace operating system commands with modified

versions that are specifically designed to ignore malicious activity

– Detecting a rootkit can be difficult10

Concealing Malware (cont’d.)

• Logic bomb – Computer program or a part of a program that lies

dormant until it is triggered by a specific logical event– Once triggered, performs malicious activities– Extremely difficult to detect before they are triggered

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Concealing Malware (cont’d.)

• Zombie– Infected ‘‘robot’’ computer

• Botnet– Hundreds, thousands, or tens of thousands of

zombies

• Internet Relay Chat (IRC) – Used to remotely control the zombies

• Number of zombies and botnets is staggering

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Hardware Attacks

• Types of hardware that is targeted includes– BIOS– USB devices– Mobile phones– Physical theft of laptop computers and information

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BIOS

• Basic Input/Output System (BIOS)– Coded program embedded on the processor chip – Recognizes and controls different devices on the

computer system

• PROM (Programmable Read Only Memory) chip– Newer computers– Flashing the BIOS

• Reprogramming

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USB Devices

• USB (universal serial bus)

• Small, lightweight, removable, and contain rewritable storage

• Common types– USB flash memory – MP3 players

• Primary targets of attacks to spread malware

• Allow spies or disgruntled employees to copy and steal sensitive corporate data

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USB Devices (cont’d.)

• Reduce the risk introduced by USB devices– Prohibit by written policy– Disable with technology

• Disable the USB in hardware

• Disable the USB through the operating system

• Use third-party software

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Mobile Phones

• Portable communication devices

• Rapidly replacing wired telephones

• Types of attacks– Lure users to malicious Web sites– Infect a mobile phone– Launch attacks on other mobile phones– Access account information– Abuse the mobile phone service

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Physical Theft

• Portable laptop computers are particularly vulnerable to theft

• Data can be retrieved from a hard drive by an attacker even after its file has been deleted

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Desktop Defences

• Defences include: – Managing patches– Installing antivirus software– Using buffer overflow protection– Protecting against theft– Creating data backups

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Managing Patches

• Patch – Software security update intended to cover

vulnerabilities that have been discovered after the program was released

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Managing Patches (cont’d.)

• Automatic update configuration options for most operating systems– Install updates automatically– Download updates but let me choose when to install

them– Check for updates but let me choose whether to

download and install them– Never check for updates

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Antivirus Software

• Scan a computer’s hard drive for infections

• Monitor computer activity

• Examine all new documents that might contain a virus

• Drawback of AV software – Must be continuously updated to recognize new

viruses

• Should be configured to constantly monitor for viruses and automatically check for updated signature files

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Buffer Overflow Protection

• Buffer overflow– Occurs when a computer process attempts to store

data in RAM beyond the boundaries of a fixed-length storage buffer

– May cause computer to stop functioning

• Windows-based system protection– Data Execution Prevention (DEP) – Address Space Layout Randomization (ASLR)

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Buffer Overflow Protection (cont’d.)

Buffer overflow attack

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Protecting Against Theft

• Applies to laptops especially

• Device lock– Steel cable and a lock

• Software tracking system

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Creating Data Backups

• Copying data from a computer’s hard drive onto other digital media – Then storing it in a secure location

• Sophisticated hardware and software can back up data on a regular schedule

• Personal computer users– Operating system functions– Third-party software

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Creating Data Backups (cont’d.)

• What information to back up– Back up only user files– Back up all files

• Frequency of backups– Regular schedule

• RAID (Redundant Array of Independent Drives)– Uses multiple hard disk drives for increased

reliability– Several RAID configurations

• Called levels

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Creating Data Backups (cont’d.)

• Backup storage media– Temporary media should not be used– Alternatives

• Portable USB hard drives

• Network Attached Storage (NAS)

• Internet services

• Disc storage

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Creating Data Backups (cont’d.)

• Location of backup storage– Protect against not only virus attacks but also

against hardware malfunctions, user error, software corruption, and natural disasters

– Backups ideally should be stored in a location away from the device that contains the information

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Recovering from an Attack

• Basic steps to perform– Disconnect– Identify– Disinfect– Recheck– Reinstall– Analyze

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Summary

• Malicious software (malware) – Enters a computer system without the owner’s

knowledge or consent – Includes a wide variety of damaging or annoying

software– Infecting malware– Concealing malware

• Hardware is also the target of attackers

• Tactics for defending desktop systems

• Basic steps to disinfect and restore a computer

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