Operating System Security

1. Operating System and
Computer Security
By,
Prof. Swati B. Bhonde,
Department of Computer Engineering
Amrutvahini College of Engineering, Sangamner

2. Why I need to have OS?

3. Software
 Operating Systems
 Run wide variety of tasks
 Run when computer is started
 Only one OS operates at a time
 Applications
 Run specified tasks
 Only run when initiated
 Can run multiple applications at a time

4. What does Operating System do
 Manages all the resource
in a computer (including
processor, memory, i/o
devices)
 Provides an interface
between the hardware
and application software.

5. Mostly used OS
 Desktop
 Windows
 Mac OS
 Unix/Linux and their siblings.
 PDA
 Palm
 Pocket PC
 Embedded Linux OS

6. Computer security challenges
 Virus
 Email Virus
 Worm
 Trojan Horse
 Spam

7. Virus
 Viruses are fragments of computer code that are linked to
the normal programs
 When normal program is infected by virus, virus will run
first every time you start the program.
 Viruses can duplicate themselves and infect other programs.
 Original virus are less and less popular now.
 People don’t copy files from others, but would rather
download from the original source.
 Anti-virus software is widely used.

9. Email virus
 An e-mail virus moves around in e-mail messages, and
usually replicates itself by automatically mailing itself to
dozens of people in the victim's e-mail address book.
 Two kinds
 Executable attachment (.exe .vbs .com .bat files).
 Macro language viruses.

10. Fact about email virus
 BOTTOM LINE :There is *NO* such thing as an E-mail
text virus!
 You can not get a virus or any system damaging
software by reading an e-mail*. E-mails (that is, the
ACTUAL message can not contain viruses)
 Email viruses always resides in the attachment. So don’t
run any suspect attachment files.

11. Worm
 A worm is a computer program that has the ability to
copy itself from machine to machine by taking
advantage of the security hole in the system.
 Security holes are bugs in the OS.
 This is the most serious threat now
 Your Computer can be infected by just plugging in the
internet.
 MSblast and SoBig are the recent worms that damage
hundreds of thousand computers.

12. Trojan Horse (back door)
 A Trojan horse is simply a
computer program. The program
claims to do one thing (it may
claim to be a game) but instead
does damage when you run it (it
may erase your hard disk).
 Trojan horse usually does replicate
itself.

13. Suggestions to secure your computer
 Use anti-virus software.
 Update your computer regularly.
 Be careful with the email attachments
 Safe: .jpg .bmp .pdf .txt ….
 Unsafe: .exe .doc .xls .ppt …
 Avoid email software by Microsoft (outlook, outlook
express…). They are mostly targeted.
 Use firewall or router to protect you from worm attack.

14. Spam (junk mail)
 Spamming is business
 Most effective way to stop it is legislation. Most states
passed law to restrict it, but none fully banned it.
 How spammers get your mail.
 Web search
 Sending test emails
 Exchange or buy from other spammers

15. Suggestions to fight spam
 Never reply junk emails
 Moreover, never even open them.
 Don’t post your actual email address in the website.
 Sparty_at_msu.edu
 Sparty@NOSPAMMINGmsu.edu
 Use a picture of your email address.
 When send group emails, put all the recipients in the
BCC field to protect other people.

16. Any questions till this part?

17. Wireless Networks and Security

18. Outline
 Wireless Networks and Security
 Attacking and defending WEP
 Attacking and defending WPA/WPA2
 Common defense techniques
 Summary

19. Wireless Networks and Security
1) What are Wireless Networks?
 A wireless network is the way that a computer is connected to a
router without a physical link.
2) Why do we need?
 Facilitates mobility – You can use lengthy wires instead, but
someone might trip over them.
3) Why security?
 Attacker may hack a victim’s personal computer and steal private
data or may perform some illegal activities or crimes using the
victim’s machine and ID. Also there's a possibility to read
wirelessly transferred data (by using sniffers)

20. Wireless Networks and Security
Three security approaches:
1. WEP (Wired Equivalent Privacy)
2. WPA (Wi-Fi Protected Access)
3. WPA2 (Wi-Fi Protected Access, Version 2)
WPA also has two generations named Enterprise and
Personal.

21. WEP (Wired Equivalent Privacy)
• Encryption:
– 40 / 64 bits
– 104 / 128 bits
24 bits are used for IV (Initialization vector)
• Passphrase:
– Key 1-4
– Each WEP key can consist of the letters "A" through "F" and the
numbers "0" through "9". It should be 10 hex or 5 ASCII
characters in length for 40/64-bit encryption and 26 hex or 13
ASCII characters in length for 104/128-bit encryption.

22. WPA/WPA2 Personal
 Encryption:
 TKIP (Temporal Key Integrity Protocol )
 AES (Advanced Encryption Standard)
 Pre-Shared Key:
 A key of 8-63 characters
 Key Renewal:
 You can choose a Key Renewal period, which instructs the
device how often it should change encryption keys. The default is
3600 seconds

23. Attacking WEP
• iwconfig – a tool for configuring wireless adapters. You can use this
to ensure that your wireless adapter is in “monitor” mode which is
essential to sending fake ARP (Address Resolution Protocol)
requests to the target router
• macchanger – a tool that allows you to view and/or spoof (fake)
your MAC address
• airmon – a tool that can help you set your wireless adapter into
monitor mode (rfmon)
• airodump – a tool for capturing packets from a wireless router
(otherwise known as an AP)
• aireplay – a tool for forging ARP requests
• aircrack – a tool for decrypting WEP keys

24. How to defend when using WEP
 Use longer WEP encryption keys, which makes the data analysis task more
difficult. If your WLAN equipment supports 128-bit WEP keys.
 Change your WEP keys frequently. There are devices that support
"dynamic WEP" which is off the standard but allows different WEP keys to
be assigned to each user.
 Use a VPN for any protocol, including WEP, that may include sensitive
information.
 Implement a different technique for encrypting traffic, such as IPSec over
wireless. To do this, you will probably need to install IPsec software on
each wireless client, install an IPSec server in your wired network, and use
a VLAN to the access points to the IPSec server.

25. Attacking WPA
• macchanger – a tool that allows you to view and/or spoof (fake) your MAC
address
• airmon – a tool that can help you set your wireless adapter into monitor
mode (rfmon)
• airodump – a tool for capturing packets from a wireless router (otherwise
known as an AP)
• aireplay – a tool for forging ARP requests
― Capture WPA/WPA2 handshakes by forcing clients to reauthenticate
― Generate new Initialization Vectors
• aircrack – a tool for decrypting WEP keys (should be used with dictionary)

26. How to defend when using WPA
 Passphrases – the only way to crack WPA is to sniff the
password PMK associated with the handshake
authentication process, and if this password is extremely
complicated it will be almost impossible to crack
 Passphrase Complexity – select a random passphrase
that is not made up of dictionary words. Select a
complex passphrase of a minimum of 20 characters in
length and change it at regular intervals

27. Common defense techniques
 Change router default user name and password
 Change the internal IP subnet if possible
 Change default name and hide broadcasting of the SSID
(Service Set Identifier)
 None of the attack methods are faster or effective when a
larger passphrase is used.
 Restrict access to your wireless network by filtering
access based on the MAC (Media Access Code)
addresses

28. Summary
 Change all possible default router settings
 Use encryption (WPA/WPA2)
 Use long and complex keys/passphrases

29. Thank you!