1. Review For Exam 3
© Abdou Illia – Spring 2016

2. Host Hardening 2

3. Computer Hardware & Software
Operating System
Web service software (IIS, Apache, ...) Web browser Productivity Software
Client & server application programs

4. Your knowledge about Host hardening
Which of the following is most likely to make a computer system unable to perform any kind of work or provide any service?
Client application programs get hacked
Server application programs (web service software, database service, network service, etc.) get hacked
The operating system get hacked
The connection to the network/Internet get shut down

5. OS Vulnerability test 2010 by omnired.com
OS tested:
Win XP, Win Server 2003, Win Vista Ultimate,
Mac OS Classic, OS X 10.4 Server, OS X 10.4 Tiger
FreeBSD 6.2, Solaris 10, Fedora Core 6, Slackware 11.0, Suse Enterprise 10, Ubuntu 6.10
Tools used to test vulnerabilities:
Scanning tools (Track, Nessus)
Network mapping (Nmap command)
All host with OS installation defaults
Results
Microsoft's Windows and Apple's OS X are ripe with remotely accessible vulnerabilities and allow for executing malicious code
The UNIX and Linux variants present a much more robust exterior to the outside
Once patched, however, both Windows and Apple’s OS are secure.
OS market share

6. Your knowledge about Host hardening
You performed an Out-of-the-box installation of Windows XP and Linux FreeBSD 6.2 on two different computers. Which computer is more likely to be secure ?
Windows XP
Linux FreeBSD 6.2
They will have the same level of security
What needs to be done, first, in order to prevent a hacker from taking over a server with OS installation defaults that has to be connected to the Internet?
Lock the server room
Configure the firewall to deny all inbound traffic to the server
Download and install patches for known vulnerabilities

7. Security Baseline
Because it’s easy to overlook something in the hardening process, businesses need to adopt a standard hardening methodology: standard security baseline
Need to have different security baseline for different kind of host; i.e.
Different security baselines for different OS and versions
Different security baselines for different types of server applications (web service, service, etc.)
Different security baselines for different types of client applications.

8. Hardening servers Choose the OS that provides the following:
Ability to restrict admin access (Administrator vs. Administrators)
Granular control of data access
Ability to disable services
Ability to control executables
Ability to log activities
Host-based firewall
Support for strong authentication and encryption
Disable or remove unnecessary services or applications
If no longer needed, remove rather than disable to prevent re-enabling
Additional services increases the attack vector
More services can increase host load and decrease performance
Reducing services reduces logs and makes detection of intrusion easier

9. Hardening servers (cont.)
Configure user authentication
Remove or disable unnecessary accounts (e.g. Guest account)
Change names and passwords for default accounts
Disable inactive accounts
Assign rights to groups not individual users
Don't permit shared accounts if possible
Configure time sync
Enforce appropriate password policy
Use 2-factor authentication when necessary
Always use encrypted authentication

10. UNIX / Linux Hardening Many versions of UNIX
No standards guideline for hardening
User can select the user interface
Graphic User Interface (GUI)
Command-Line Interfaces (CLIs) or shells
CLIs are case-sensitive with commands in lowercase except for file names

11. UNIX / Linux Hardening Three ways to start services
Start a service manually (a) through the GUI, (b) by typing its name in the CLI, or (c) by executing a batch file that does so
Using the inetd program to start services when requests come in from users
Using the rc scripts to start services automatically at boot up
Inetd = Internet daemon; i.e. a computer program that runs in the background

12. UNIX / Linux Hardening Starting services upon client requests
Services not frequently used are dormant
Requests do not go directly to the service
Requests are sent to the inetd program which is started at server boot up
Program A
1. Client Request
To Port 123
4. Start and
Process
This Request
Program B
inetd
Program C
Program D
2. Port 123
3. Program C
Port Program A
Port Program B
Port Program C
Port Program D
/etc/inetd.config

13. UNIX / Linux Hardening
Turning On/Off unnecessary Services In UNIX
Identifying services running at any moment
ps command (process status), usually with –aux parameters, lists running programs
Shows process name and process ID (PID)
netstat tells what services are running on what ports
Turning Off Services In UNIX
kill PID command is used to kill a particular process
kill (If PID=47)

14. Advanced Server Hardening Techniques
File Integrity Checker
Creates snapshot of files: a hashed signature (message digest) for each file
After an attack, compares post-hack signature with snapshot
This allows systems administrator to determine which files were changed
Tripwire is a file integrity checker for Linux/UNIX, Windows, etc.: (ftp://coast.cs.purdue.edu/pub/tools/unix)

15. Advanced Server Hardening Techniques
Reference Base
File 1
File 2 …
Other Files in
Policy List
File 1 Signature
File 2 Signature … 1.
Earlier
Time
Tripwire
3. Comparison to Find Changed Files
Post-Attack Signatures
File 1
File 2 …
Other Files in
Policy List
File 1 Signature
File 2 Signature … 2.
After
Attack
Tripwire
File Integrity problem: many files change for legitimate reasons. So it is difficult to know which ones the attacker changed.

16. The Elements of Cryptography

17. Cryptography? Traditionally, cryptography refers to
The practice and the study of encryption
Transforming information in order to prevent unauthorized people to read it.
Today, cryptography goes beyond encryption/decryption to include
Techniques for making sure that encrypted messages are not modified en route
Techniques for secure identification/authentication of communication partners.

18. Your knowledge about Cryptography
Which of the following do cryptographic systems protect?
Data stored on local storage media (like hard drives) from access by unauthorized users.
Data being transmitted from point A to point B in a network
Both a and b

19. Your knowledge about Cryptography
Which of the following security issues is addressed by cryptographic systems?
Confidentiality; i.e. protection against eavesdropping
Authentication; i.e. assurance parties involved in a communication are who they claim to be
Message integrity; i.e. assurance that messages are not altered en route
Availability; i.e. making sure that communication systems are not shut down by intruders.
All of the above

20. Basic Terminology 1
Plaintext: original message to be sent. Could be text, audio, image, etc.
Encryption/Decryption Algorithm: mathematical tool (software) used to encrypt or decrypt
Key: A string of bits used by to encrypt the plaintext or decrypt the ciphertext
Ciphertext: encrypted message. Looks like a random stream of bits
Encryption
Algorithm
+ Encryption key
Hello
Ciphertext “ ”
Plaintext
“Hello”
Network
Interceptor
Party A
Decryption
Algorithm
Plaintext
“Hello”
Ciphertext “ ”
+ Decryption key
Party B

21. Free Encryption online: Tools4noobs.com
Basic Terminology 2
Encryption:
Converting plaintext into ciphertext using algorithms and keys
The size of the ciphertext is proportional to the size of the plaintext
Ciphertext is reversible to plaintext
Symmetric Key Encryption:
Same key is used both for encryption and decryption
Keys are usually identical or trivially identical*
Asymmetric Key Encryption:
Also called Public/Private Key Encryption
Two different keys are used: one for encryption, one for decryption
* Trivially identical means simple transformation could lead from one key to the another.
Party A
Party B
Party A
Party B
Free Encryption online: Tools4noobs.com

22. Your knowledge about Cryptography
Based on how symmetric encryption systems work, which of the following is the worst thing to happen?
An attacker gets a copy of the encryption and decryption algorithms
An attacker gets the decryption key
a and b are equally damaging
Which of the following presents more challenge for exchanging keys between partners?
Asymmetric encryption
Symmetric encryption
A and b are equally challenging

23. Exhaustive search and Key length
Attacker could use the right algorithm and do an exhaustive search (i.e. try all possible keys) in order to decrypt the ciphertext
Most attacks require the capture of large amount of ciphertext
Every additional bit in the length of the key doubles the search time
Every additional bit in the length of the key doubles the requirements in terms of minimum processor’s speed to crack the key.
Key Length in bits
Number of possible keys (2key length in bits) 1 2 4 16 8
256
65536 56
112
or E+33
168
E+50
E+77
512
1.3408E+154

24. Your knowledge about Cryptography
If you increase the key length from 56 bits to 66 bits. How much more key combinations an attacker who captures enough ciphertext will have to try in order to decipher the captured ciphertext using the appropriate algorithm?
_______________________________________
Assuming that it takes 7 days to try all possible combinations of a 56 bit key, how much time it would take to try all possible combinations when the key length is increased to 58 bits?
________________

25. Weak vs. Strong Keys Symmetric Key Encryption
Usually for private of customer e-business
Keys < 100-bit long are considered weak today.
Keys 100-bit long or more are considered strong today.
Asymmetric Key Encryption
Usually used for B2B e-commerce
Key pairs must be much longer (512 bit and more) because of the disastrous consequences of breaking the decryption key
Key Length in bits
Number of possible keys (2key length in bits)
Type of communication 1
21 = 2 2
22 = 4 16
216 = 65536 56
256 =
Private, symmetric, weak asymmetric (e.g. DES)
100
2100 =
Private, symmetric
112
2112 = or E+33
Business, asymmetric (e.g. 112-bit DES)
168
E+50
Business, asymmetric (e.g. 3DES)
256
E+77
Business, asymmetric (e.g. AES)
512
1.3408E+154
Business, asymmetric (e.g. RSA)
1024 to 4096
21024 to 24096

26. Your knowledge about Cryptography
Most attacks require the capture of large amount of ciphertext, which can take a certain amount of time. Beside using strong keys what else can be done to make it harder to crack the key?
Answer: change the key very often

27. Symmetric Key Encryption

28. Symmetric Key Encryption methods
Two categories of methods
Stream cipher: algorithm operates on individual bits (or bytes); one at a time
Block cipher: operates on fixed-length groups of bits called blocks
Only a few symmetric methods are used today
Methods
Year approved
Comments
Data Encryption Standard - DES
1977
1998: Electronic Frontier Foundation’s Deep Crack breaks a DES key in 56 hours
DES-Cipher Block Chaining
Triple DES – TDES or 3DES
1999
Advanced Encryption Standard – AES
2001
Its versions among the most used today
Other symmetric encryption methods
IDEA (International Data Encryption Algorithm), RC5 (Rivest Cipher 5), CAST (Carlisle Adams Stafford Tavares), Blowfish

29. Data Encryption Standard (DES)
DES is a block encryption method, i.e. uses block cipher
DES uses a 64 bit key; actually 56 bits + 8 bits computable from the other 56 bits
Problem: same input plaintext gives same output ciphertext
DES Encryption
Process
64-Bit Ciphertext
Block
64-Bit DES Symmetric Key
(56 bits + 8 redundant bits)
64-Bit Plaintext

30. DES-Cipher Block Chaining
DES-CBC uses ciphertext from previous block as input making decryption by attackers even harder
An 64-bit initialization vector is used for first block
First
64-Bit Plaintext Block
DES Key
Initialization
Vector (IV)
DES Encryption
Process
Second
64-Bit Plaintext Block
DES Key
First
64-Bit Ciphertext Block
DES Encryption
Process
Second
64-Bit Ciphertext Block

31. 168-Bit Encryption with Three 56-Bit Keys
Triple DES (3DES)
168-Bit Encryption with Three 56-Bit Keys
Sender
Receiver
Encrypts original plaintext with the
1st key
Decrypts ciphertext with
the 3d key
1st
3rd
Decrypts output of first
step with the 2nd key
Encrypts output of the
first step with the 2nd key
2nd
2nd
Encrypts output of second
step with the 3d key; gives
the ciphertext to be sent
Decrypts output of second
step with the 1st key; gives
the original plaintext
3rd
1st

32. 112-Bit Encryption With Two 56-Bit Keys
Triple DES (3DES)
112-Bit Encryption With Two 56-Bit Keys
Sender
Receiver
Encrypts plaintext with the
1st key
Decrypts ciphertext with
the 1st key
1st
1st
Decrypts output with the
2nd key
Encrypts output with the
2nd key
2nd
2nd
Encrypts output with the
1st key
Decrypts output with the
1st key
1st
1st

33. Your knowledge about Cryptography
Based on the way DES and 3DES work, which of the following is true?
3DES requires more processing time than DES
Compared 3DES, DES requires more RAM
Both a and b
Given the increasing use of hand-held devices, 3DES will be more practical than DES.
True
False

34. Advanced Encryption Standard - AES
Developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen, and submitted to the AES selection process under the name "Rijndael", a portmanteau of the names of the inventors
Offers key lengths of 128 bit, 192 bit, and 256 bit
Efficient in terms of processing power and RAM requirements compared to 3DES
Can be used on a wide variety of devices including
Cellular phones
PDAs
Etc.

35. Asymmetric Key Encryption

36. Public Key Encryption For confidentiality
Each Party uses other party’s public key for encryption
Each Party uses own private key for decryption
No need to exchange private key, but key needs to be very strong (512+ bit)
Party A
Party B
Decrypt with
Party A’s Private Key
Encrypt with
Party A’s Public Key
Party B’s Public Key
Party B’s Private Key
Encrypted
Message

37. Public Key Encryption methods
Asymmetric encryption methods are used both for
Encryption in order to provide confidentiality
Digital signature in order to provide partners’ authentication
Methods
Year proposed
Comments
RSA by Ron Rivest, Adi Shamir, and Leonard Adleman
1977
1995: First attack in lab conditions was reported
Elliptic Curve Cryptosystem - ECC
1985
Becoming widely used
Other symmetric encryption methods:
Dieffe-Hellman, El-Gamal

38. Basic Terminology 3 Hashing: Hash function: Hash:
Mathematical process for converting inputs into fixed-length outputs
Hash function:
Algorithm that does the hashing. Uses an input + a shared secret or password. Example: MD5, Secure Hash Algorithm.
Hash:
Fixed-length output of the hashing

39. Encryption Versus Hashing
Use of Key
Uses a key as an
input to an
encryption method
Password is usually added
to text; the two are
combined, and the
combination is hashed
Length of
Result
Output is similar in
length to input
Output is of a fixed
short length,
regardless of input
Reversibility
Reversible; ciphertext
can be decrypted
back to plaintext
One-way function; hash
cannot be “de-hashed” back
to the original string

40. Cryptographic Systems (cont.)
Packaged set of cryptographic countermeasures used for protecting dialogues

41. MS-CHAP* Hashing for Authentication
CHAP is an authentication hashing scheme used by Point to Point Protocol (PPP) servers to validate the identity of remote clients
After the completion of the link establishment phase, the server sends a "challenge" message to the client.
The client responds with a value calculated using a one-way hash function, such as an MD5 or SHA (Secure Hash Algorithm).
The server checks the response against its own calculation of the expected hash value. If the values match, the server acknowledges the authentication; otherwise it should terminate the connection.
At random intervals the server sends a new challenge to the peer and repeats steps 1 through 3.
Shared secret
* Microsoft’s version of Challenge Handshake Authentication Protocol

42. MD5 (Message-Digest algorithm 5)
A widely used cryptographic hash function used to hash inputs (typed texts or files) in order to generate hash values (called checksums, message digest, or output)
An MD5 hash value is typically expressed as a 16- hexadecimal number like 912df11644fccac439b6fc5f80af5cdb
Each hex number is 8 bits
MD5 generates a 128-bit hash value regardless of the input length.
Commonly used to check the integrity of files like downloaded software programs 42

43. SHA1 (Secure Hash Algorithm 1)
A widely used cryptographic hash function used to hash inputs (typed texts or files) in order to generate hash values (called checksums, message digest, or output)
A SHA1 hash value is typically expressed as a 20-hexadecimal number like fb1a26e4bc422aef54eb4
SHA1 generates a 160-bit hash value regardless of the input length
Commonly used to check the integrity of files like downloaded software programs 43

44. Application Security: General apps &Web service

45. General Applications Security Issues

46. Which of the following is true about Application Security?
If a server application (or service) is no longer needed, it should be turned off
Fewer applications on a computer means fewer attack opportunities
Use good security baselines to install and configure apps
Do not install application centrally using group policies
Add application layer authentication by requiring users to provide credentials to run application programs
Implement cryptographic authentication for sensitive apps
If a server application (or service) is no longer needed, it should be removed
Do not turn on each applications’ automatic update checking 46

47. Applications and Buffer Overflow
OUTDO OR
Buffers are RAM areas where data is stored temporarily
Buffer overflow occurs when data spill from one buffer to the next
Buffer Overflow is the biggest issue in application coding
If an attacker sends more data than the programmer had allocated to a buffer, a buffer might overflow, overwriting an adjacent section of RAM
Buffer overflow attacks
RAM
Buffer1
Buffer2
Buffer7
Buffer3
Buffer4
Buffer6
Buffer5 47

48. Buffer Overflow Attack
Occurs when ill-written programs allow data destined to a memory buffer to overwrite instructions in adjacent memory register that contains instructions.
If the data contain malware, the malware could run and creates a DoS
Example of input data: ABCDEF LET JOHN IN WITHOUT PASSWORD
Buffer
Instructions 1 2 3 4 5 6
Print
Run Program
Accept input
Buffer
Instructions 1 2 3 4 5 6 A B C D E F
LET JOHN IN WITHOUT PASSWORD
Run Program
Accept input 48 48

49. Preventing Buffer Overflow
Key Principle: Never Trust User Input
Use Languages/tools that provide automatic bounds checking such as Perl, Python, and Java instead lower level language (C or Assembly, etc).
However, this is usually not possible or practical because almost all modern OS are written in the C language.
Eliminate The Use Of Flawed Library Functions like gets(), strcpy, and strcmp that fail to check the length or bounds of their arguments.
Design And Build Security Within Code
Use Source Code Scanning Tools.
Example: PurifyPlus Software Suite can perform a dynamic analysis of Java, C, or C++ source code.
For instance, this simple change informs strcpy() that it only has an eight byte destination buffer and that it must discontinue raw copy at eight bytes.
// replace le following line
strcpy (buffer2, strng2);
// by
strcpy (buffer2, string2, 8)

50. Web service security

51. Webservice & E-Commerce apps
Web applications could be the target of many types of attacks like:
Directory browsing
Traversal attacks
Web defacement
Using HTTP proxy to manipulate interaction between client and server
IIS IPP Buffer Overflow
Browser attacks
Time configuration

52. Web sites’ directory browsing
Web server with Directory Browsing disabled
User cannot get access to list of files in the directory by knowing or guessing directory names

53. Web site with directory browsing
Web server with Directory Browsing enabled
User can get access to the list of files in the directory by knowing or guessing directory names

54. Traversal Attack Normally, paths start at the WWW root directory
Adding ../ (Windows) or ..\ (Unix) in an HTTP request might take the attacker up a level, out of the WWW root directory.
Example: ../../
Example:
If attacker traverses to Command Prompt directory in Windows or NT, he can execute any command with system privileges

55. Traversal Attacks (Cont.)
Preventing traversal attacks
Companies filter out ../ and ..\ using URL scanning software
Attackers respond with hexadecimal and UNICODE representations for ../ and ..\
ASCII Character Chart with Decimal, Binary and Hexadecimal Conversions
Name
Character
Code
Decimal
Binary
Hex
Null
NUL 00
Start of Heading
SOH
Ctrl A 1 01
Space 32 20
Exclamation Point !
Shift 1 33 22
Plus +
Shift = 43 2B
Period . 46 2E
Forward Slash / 47 2F
Tilde ~
Shift’
126 7E

56. IIS IPP Buffer Overflow
The Internet Printing Protocol (IPP) service included in IIS 5.0 and earlier versions is vulnerable to buffer overflow attacks
The jill.c program was developed to launch the attack using:
GET NULL.printer HTTP/1.0
Host: 420-byte jill.c code to launch the command shell
IIS server responds launching the command shell (C:\WINNT\SYSTEM32\>) giving the attacker SYSTEM privileges.

57. IIS IPP Buffer Overflow (cont.)
Link to jill.c code
Code compilable using gcc jill.c –o jill on Linux
Precompiled version (jill-win32.c) and executable (jill-win32.exe) available at ftp://ftp.technotronic.com/
newfiles/jill-win32.exe. This executable file is ready to run on a Windows machine.

58. Browser Attacks Malicious links attack.txt.exe seems to be attack.txt
User must click on them to execute (but not always)
Common extensions are hidden by default in some operating systems.
attack.txt.exe seems to be attack.txt