1. Outcomes Why are computer networks vulnerable?
Methods used by hacker to gain unauthorised access
Viruses
Different type of viruses
How do viruses infect computers
Methods used by anti-virus software
Symptoms of virus infection
Steps to take to protect your computer from viruses

2. Brief History of Computer Security
With the explosive growth of the
Internet, there has been a rise in
importance of computer security

3. Why are networked systems vulnerable.
Internet is 37 years old
Was designed without security provisions
Communication protocols (TCP/IP) were designed when the security was not an issue.
Security features had to be layered at the top of the design
Old operating systems were design for a single user
No security was need
Explosive growth of desktops started in ’80s
Also no emphasis on security
Explosive growth started in mid-’90s
Security not a priority until much later

4. Computer security was ignored
Interest in computer security very old
But largely confined to the military
Other communities did not care
Internet - it’s only a research network, who would attack it?
Desktops - who needs military security, I just want to run my spreadsheet!

5. Important event Morris worm - 1988 E-commerce - mid ‘90s
Brought down a large fraction of the Internet
Academic interest in network security
E-commerce - mid ‘90s
Industrial interest in network security protocols
Resurgence of worms - early ‘00s
Made computer security a household term

6. Modern operating systems
Improved security in modern operating systems
Challenge for hackers
Hackers did not give up
more sophisticated virus were born.
Security is still a major issue in networked systems

7. Unauthorised logins and password stealing
Intruders use various ways to access someone’s account
Brute force:
Program making successive login attempts
Domain knowledge:
Users tend to use passwords easy to remember
Partner’s name, …
Mock login:
If a hacker has physical access, they might install a program simulate the screen image of the login prompt and store userid/password.
Human factors:
Call the computer help desk claiming you forgot your password.
Reformed hackers, the best way to get information is to ask for it.
Spyware:
malicious code that gains access to a computer via a Trojan Horse
can monitor the user’s keystrokes and report passwords, credit card numbers
etc to the hacker via a TCP/IP connection

8. Viruses

9. Virus Statistics 1988: Less than 10 known viruses
1990: New virus found every day
1993: new viruses per week
1999: 45,000 viruses and variants

10. A Couple of Definitions:
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.
“a program that replicates by “infecting” other programs, so that they contain a copy of the virus”

11. How
Viral code is attached or “inserted” into the order of execution so that when the legitimate code is run the viral code is also run or run instead of the legitimate code.
May be “tacked” on to the end of an executable file or inserted into unused program space.
Cavity viruses:
Overwrite part of a legitimate program
Hard to detect as file size is not modified
Overwrite boot records:
Viruses starts executing when the computer starts up

12. The Normal Virus works like this:
User call for a legitimate program
The virus code, having inserted itself in the order of execution, executes instead or in addition to the legitimate program.
The virus code terminates and returns control to the legitimate program

13. How they work: Basic structure: {
look for one or more infectable objects
if (none found)
exit
else
infect object }
Doesn’t remain in memory, but executes all of the viral code at once then returns control to the infected program

14. Worms
A computer WORM:
is a self-contained program (or set of programs), that is able to spread functional copies of itself or its segments to other computer systems via network connections. 
worms do not need to attach themselves to a host program.
2 types of worms
host computer worms
network worms. 

15. NETWORK- Computer Worms
 Network worms consist of multiple parts, called segments.
The segments run on different machines on the network
and may even perform different actions
Moving a segment from one machine to another is only one of their purposes.

16. HOST- Computer Worms Host computer worms:
are entirely contained in the computer they run on.
use network connections only to copy themselves to other computers.
the original terminates after it launches a copy on to another host.
Only one copy of the worm running somewhere on the network at a time

17. How Viruses are born
Unlike biological viruses, computer viruses do not simply evolve by themselves
deliberately created by programmers, or by people who use virus creation software

18. How Viruses are born
Viruses are written as
research projects
to attack the products of specific companies,
to distribute political messages,
and financial gain from identity theft,
Some virus writers
consider their creations to be works of art
See virus writing as a creative hobby
Releasing computer viruses is a crime in most jurisdictions

19. Viruses can avoid detection
To avoid detection by users, viruses employ different deception methods
They do not make themselves to
change the date of last modified
increase file sizes
damage the files
They kill the tasks associated with antivirus software before it can detect them

20. Logic Bomb:
Logic Bomb: A logic bomb executes when specific conditions occur.
Triggers for logic bombs can include change in a file, by a particular series of keystrokes, or at a specific time or date.

21. Trapdoor
Trapdoors allow access to a system by skipping the usual login routine.
Overall goal of rootkits: install trapdoors

22. Macro Viruses Macro virus:
Encoded as macro and embedded in a document.
Many applications allows you to embed a macro in a document.
Microsoft Word, Excel, Access
The macro executes each time the document is open.
Infect programming environments rather than files
Once a macro virus gets onto your machine, it embedded itself in all future documents you create with the application
75% of all viruses today are macro viruses

23. Why are they so dangerous?
Can infect multiple types of operating systems
People don’t normally think of viruses in documents
Easy to learn how to write a macro virus
Because office programs are usually integrated, programs can be used to further spread the virus

24. Famous Macro Viruses Concept: - Distributed by Microsoft
Considered to be the first macro virus
Simply showed the potential for macro viruses

25. History of some well known Viruses
1999 The Melissa virus:
is a macro virus,
It uses Microsoft Word to infect computers and is passed on to others through Microsoft Outlook and Outlook Express programs
Overwrites first macro in open documents and in the normal.dot template
Turns off macro detection

26. Viruses (Con’t) 2000 The "I Love You Virus"
wreaks havoc around the world.
It is transmitted by and when opened, is automatically sent to everyone in the user's address book

27. July 2001: The Code Red worm
infects tens of thousands of systems running Microsoft Windows NT and Windows 2000 server software.
causing an estimated $2 billion in damages.
The worm is programmed to use the power of all infected machines against the White House Web site at a predetermined date.
the White House deciphers the virus's code and blocks traffic as the worm begins its attack. .

28. Viruses (con’t)
2002: Melissa virus author David L. Smith, 33, is sentenced to 20 months in federal prison
Jan. 2003: The "Slammer" worm
infects hundreds of thousands of computers in less than three hours.
The fastest-spreading worm ever wreaks havoc on businesses worldwide, knocking cash machines offline and delaying airline flights.

29. Viruses (Con’t) 26 January 2004, MyDoom:
The Mydoom virus is first identified around 8am.
Computer security companies report that Mydoom is responsible for approximately one in ten messages at this time.
Slows overall internet performance by approximately ten percent and average web page load times by approximately fifty percent
1 February: An estimated one million computers around the world infected with Mydoom begin the virus's massive distributed denial of service attack—the largest such attack to date

30. Virurses (Con’t) 2007: A new virus called "Storm Worm." is released.
This fast-spreading spammer disguises itself as a news and asks you to download film.
The "Storm Worm" gathers infected computers into a botnet, which it uses to infect other machines.
It was first identified on Jan. 17 and within 13 days had infected 1.7 million computers

31. 9 million computers running on Windowsoperating system were hit.
2009 "Conficker" worm:
9 million computers running on Windowsoperating system were hit.
The malware spread via the Internet and the main tools that helped the worm spread were unpatched corporate networks and USB memory sticks.
t loads itself on to a computer by exploiting a weakness in Windows servers.
Once it has infected a machine, the software also tries to connect to up to 250 different domains with random names every day.

32. Other type of viruses Trojan horse Denial of service (Dos)
Distributed DoS attacks
Remote Administration Trojans (RATs)
Buffer Overflow attack

33. The Original Trojan Horse
Trojan horses are named after Homer’s Iliad story of Greeks gifting a huge wooden horse to Troy that housed soldiers who emerged in the night and attacked the city.

34. Trojan Horses
Trojan horses are programs that appear to have one function but actually perform another function.
Modern-day Trojan horses resemble a program that the user wishes to run - a game, a spreadsheet, or an editor. While the program appears to be doing what the user wants, it is also doing something else unrelated to its advertised purpose, and without the user's knowledge.

35. Denial-of-Service (DoS) Attacks
Prevent a system from servicing legitimate requests
In many DoS attacks, unauthorized traffic saturates a network’s resources, restricting access for legitimate users
Typically, attack is performed by flooding servers with data packets
Usually require a network of computers to work simultaneously, although some skillful attacks can be achieved with a single machine
Can cause networked computers to crash or disconnect, disrupting service on a Web site or even disabling critical systems such as telecommunications or flight-control centers

36. Distributed DoS attacks
Programs of this type
Spread to as many hosts as possible
Wait for predefined commands or fixed date and time to lunch denials of Service

37. Remote Administration Trojans (RATs)
Once installed on PC.
Give hackers complete control
They can record keystrokes, web access, copy/delete files
RATs consists of client and server:
The server somehow installed on the victim’s computer
Attempt to contact the hacker’s system (client)

38. Software Exploitation
Buffer overflow attacks
Occurs when an application sends more data to a buffer than it can hold
Can push the additional data into adjacent buffers, corrupting or overwriting existing data
A well-designed buffer overflow attack can replace executable code in an application’s stack to alter its behavior
May contain malicious code that will then be able to execute with the same access rights as the application it attacked
Depending on the user and application, the attacker may gain access to the entire system

39. Buffer Overflow Injection
buffer overflow, or buffer overrun,
is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory.
can be triggered by inputs that are designed to execute code, or alter the way the program operates
Steps
Inject attack code into buffer
Redirect control flow to attack code
Execute attack code .

40. Types of Propagation Parasitic Boot sector infectors
Propagates by being a parasite on other files.
Attaching itself in some manner that still leaves the original file usable.
.com and .exe files of MS-DOS
Macro virus
Boot sector infectors
Copy themselves to the bootable portion of the hard (or floppy) disk.
The virus gains control when the system is booted.

41. How Antivirus software works?
Detect using a list of virus signature definitions
comparing the files stored on fixed or removable drives (hard drives, floppy drives), against a database of known virus "signatures".

42. How Antivirus software works?
Heuristic detection:
Use a heuristic algorithm to find viruses based on common behaviors
Looks for code which is similar to known viruses
Or monitor suspicious activities
Attemting to write to system files or boot records.

43. How Antivirus software works?
File size changes:
Are monitored
Difficult to detect cavity viruses as the file size will not necessarily change.

44. How Antivirus software works?
Some anti-virus programs gives you a real time protection
Examin files as they are being opened, downloaded, copied, accessed, and transmitted etc

45. How Antivirus software works?
They need regular updates
in order to gain knowledge about the latest threats

46. Damage prevention & data recovering
How to prevent damages caused by viruses?
Take regular backups (including OS) on different media, unconnected to the system (most of the time)

47. Keep your computer Virus free
Install reliable anti-virus software
the most important step you can take towards keeping your computer clean of viruses
Update your anti-virus software regularly
variations of viruses and new ones can be slipped if your software is not current

48. Keep your computer Virus free
Get immediate protection
Configure your anti-virus software to boot automatically on start-up and run at all times

49. Keep your computer Virus free
Don't automatically open attachments
ensure that you examine and scan and other attachments before they run as they might contain viruses
Activate macro virus protection in your word processor
Check security setting in your web browser.
Scan all incoming attachments
Do not open any attached files if the subject line is questionable, unexpected or the source (address) is unknown, suspicious or untrustworthy

50. Keep your computer Virus free
Delete chain s and junk
Do not forward or reply to any of them, they clogs up the network
Some viruses can replicate themselves and spread through as a chain

51. Symptoms of virus infections
Delay in start up, loading files and programs
Increase in program size files
Shortage of disk space or memory
New file names or file dates/times
Files deleted unexpectedly
Computer crashes
Message or images appearing on the screen
Ms-word macro protection warns that a file contains macros.
Anti-virus software reports a virus

52. Summary Computer network are vulnerable
Methods used by hacker to gain unauthorised access
Viruses
Different type of viruses
How do viruses infect computers
Methods used by anti-virus software
Symptoms of virus infection
Steps to take to protect your computer from viruses

53. Resources Symantec Anti-virus centre
Centre for computing and social Responsibility (CCSR)
CERT: Centre at Carnegie-Mellon University USA
Risks forum: online discussion about security issues
CIAC: site hosted by US Dept of Energy
Dealing with hoax virus alerts
Microsoft:

54. Thank you
And
Good luck