Security R U Totally Secure !
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The document covers various aspects of computer security, including threats, user authentication, and cryptography as tools for protection. It discusses types of security attacks, such as trojan horses, viruses, and denial of service, along with strategies for defending against them, such as firewalls and encryption standards. It also highlights the importance of strong password management and outlines how modern security systems, including SSL/TLS protocols, secure communications over networks.
![SECURITY
Example of Buffer Overflow Waiting To Happen:
#include <stdio.h>
#define BUFFER SIZE 256
int main(int argc, char *argv[])
{
char buffer[BUFFER SIZE];
int other_data;
if (argc < 2)
return -1;
else {
strcpy(buffer,argv[1]);
return 0;
}
}
15:Security
8
Typical Security Attacks](https://image.slidesharecdn.com/section15-security-150622034152-lva1-app6891/85/Security-R-U-Totally-Secure-8-320.jpg)
![SECURITY
AN EXAMPLE:
Separate the text to be encoded into chunks with values 0 - ( n - 1 ).
15:Security
23Public Key Cryptosystems
In our example, we'll use < space = 0, A = 1, B = 2, C = 3, D = 4, E = 5 >.
Then " B A D <sp> B E E " --> "21 04 00 25 05"
21 ^ 17 ( mod 33 ) = 21. 21 ^ 13 ( mod 33 ) = 21.
04 ^ 17 ( mod 33 ) = 16. 16 ^ 13 ( mod 33 ) = 04.
00 ^ 17 ( mod 33 ) = 00. 00 ^ 13 ( mod 33 ) = 00.
25 ^ 17 ( mod 33 ) = 31. 31 ^ 13 ( mod 33 ) = 25.
05 ^ 17 ( mod 33 ) = 14. 14 ^ 13 ( mod 33 ) = 05.
This whole operation works because, though n and Ke are known, p and q are not
public. Thus Kd is hard to guess.
[Note: recently a 100 digit number was successfully factored into two prime numbers.]](https://image.slidesharecdn.com/section15-security-150622034152-lva1-app6891/85/Security-R-U-Totally-Secure-23-320.jpg)
Security R U Totally Secure !
- 1. 1
- 2. SECURITY In This Chapter: The Security Problem Program Threats System and Network Threats Cryptography as a Security Tool User Authentication Implementing Security Defenses Firewalling to Protect Systems and Networks Computer-Security Classifications An Example: Windows XP 15:Security 2
- 3. SECURITY SECURITY ISSUES: External protection of a system. A classified site goes to extraordinary lengths to keep things physically tight. Among the issues to be considered: Unauthorized access Mechanism assuring only authorized individuals see classified materials. Malicious modification or destruction Accidental introduction of inconsistency. Authentication How do we know the user is who she says she is. Can have passwords on domains. 15:Security 3 Protection of passwords is difficult. Issues include: • It's very easy to guess passwords since people use simple and easily remembered words. • Need exists to change passwords continually. • Limiting number of tries before locking up.
- 4. SECURITY 15:Security 4Security Issues Trojan Horse: A piece of code that misuses its environment. The program seems innocent enough, however when executed, unexpected behavior occurs. Trap Doors: Inserting a method of breaching security in a system. For instance, some secret set of inputs to a program might provide special privileges. Threat monitoring: Look for unusual activity. Once access is gained, how do you identify someone acting in an unusual fashion? Audit Log: Record time, user, and type of access on all objects. Trace problems back to source. Worms Use spawning mechanism; standalone programs. Internet Worm: In the Internet worm, Robert Morse exploited UNIX networking features (remote access) as well as bugs in finger and sendmail programs. Grappling hook program uploaded main worm program. Viruses Fragment of code embedded in a legitimate program. Mainly effects personal PC systems. These are often downloaded via e-mail or as active components in web pages. Firewall A mechanism that allows only certain traffic between trusted and un- trusted systems. Often applied to a way to keep unwanted internet traffic away from a system.
- 5. SECURITY ATTACK METHODS: Attacks on a distributed system include: Passive wiretapping. ( unauthorized interception/reading of messages ) Active wiretapping: Modification Changing a portion of the message. Spurious messages Introducing bogus messages with valid addresses and consistency criteria. Site impersonation Claiming to be some other logical node. Replay of previous transmission - repeating previous valid messages. (for example, authorization of cash withdrawal.) 15:Security 5Typical Security Attacks
- 7. SECURITY ATTACK METHODS: Trojan Horse Code segment that misuses its environment Exploits mechanisms for allowing programs written by users to be executed by other users Spyware, pop-up browser windows, covert channels Trap Door Specific user identifier or password that circumvents normal security procedures Could be included in a compiler Logic Bomb Program that initiates a security incident under certain circumstances Stack and Buffer Overflow Exploits a bug in a program (overflow either the stack or memory buffers) 15:Security 7 Typical Security Attacks
- 8. SECURITY Example of Buffer Overflow Waiting To Happen: #include <stdio.h> #define BUFFER SIZE 256 int main(int argc, char *argv[]) { char buffer[BUFFER SIZE]; int other_data; if (argc < 2) return -1; else { strcpy(buffer,argv[1]); return 0; } } 15:Security 8 Typical Security Attacks
- 9. SECURITY Viruses Code fragment embedded in legitimate program Very specific to CPU architecture, operating system, applications Usually borne via email or as a macro Visual Basic Macro to reformat hard drive Sub AutoOpen() Dim oFS Set oFS = CreateObject(’’Scripting.FileSystemObject’’) vs = Shell(’’c:command.com /k format c:’’,vbHide) End Sub 15:Security 9 Typical Security Attacks
- 10. SECURITY A Boot Sector Virus 15:Security 10 Typical Security Attacks
- 11. SECURITY System And Network Threats Worms – use spawn mechanism; standalone program Internet worm Exploited UNIX networking features (remote access) and bugs in finger and sendmail programs. (See next slide) Grappling hook program uploaded main worm program Port scanning Automated attempt to connect to a range of ports on one or a range of IP addresses Denial of Service Overload the targeted computer preventing it from doing any useful work Distributed denial-of-service (DDOS) come from multiple sites at once 15:Security 11 Typical Security Attacks
- 12. SECURITY Stuxnet 15:Security 12 Stuxnet is a computer worm discovered in June 2010. It initially spreads via Microsoft Windows, and targets Siemens industrial software and equipment. Different variants of Stuxnet targeted five Iranian organizations, with the probable target widely suspected to be the uranium enrichment infrastructure in Iran. It is initially spread using infected removable drives such as USB flash drives, and then uses other exploits and techniques to infect and update other computers inside private networks that are not directly connected to the Internet. The malware has both user-mode and kernel-mode rootkit capability under Windows, and its device drivers have been digitally signed with the private keys of two certificates that were stolen from two separate companies. The driver signing helped it install kernel mode rootkit drivers successfully and therefore remain undetected for a relatively long period of time. Once installed on Windows Stuxnet infects files belonging to Siemens' control software[3 and subverts a communication library. Doing so intercepts communications between software running under Windows and the target Siemens devices. The malware can install itself on PLC devices unnoticed. Stuxnet malware periodically modifies a control frequency to and thus affects the operation of the connected centrifuge motors by changing their rotational speed. Siemens Simatic S7-300 PLC CPU with three I/O modules attached
- 13. SECURITY Password stealing – Easiest way is through social means fake deposit slips easily guessable passwords calling people on the phone and asking for passwords (or Credit Card numbers, for that matter) – Technological approaches also simple one: leave program running on a terminal that fakes the login sequence. Capture user name and password to a file and then exit with a fake error message, returning control to the real login process – Unix password files used to be openly available (encrypted password). Lends itself to brute-force cracking. Unfortunately some programs require access to the password file to run (e.g., mail) also unfortunately Unix only uses first eight characters of password 15:Security 13 Authentication SecurID – uses a preprogrammed string of characters
- 14. SECURITY Password stealing – Easiest way is through social means fake deposit slips easily guessable passwords calling people on the phone and asking for passwords (or Credit Card numbers, for that matter) – Technological approaches also simple one: leave program running on a terminal that fakes the login sequence. Capture user name and password to a file and then exit with a fake error message, returning control to the real login process – Unix password files used to be openly available (encrypted password). Lends itself to brute-force cracking. Unfortunately some programs require access to the password file to run (e.g., mail) also unfortunately Unix only uses first eight characters of password 15:Security 14 Authentication SecurID – uses a preprogrammed string of characters
- 15. SECURITY 15:Security 15 NSA Exploitation Edward Snowden made public documents that reveal Government agencies: •consider it essential to be able to view encrypted data •have adopted a battery of methods in their assault on this biggest threats Those methods include •control over setting of international encryption standards, •the use of supercomputers to break encryption with "brute force", •Collaboration with technology companies and internet service providers themselves •“Man in the middle” attacks on the communication channels themselves.
- 16. SECURITY DEFINITIONS: Encryption: C = E( M, Ke ) E = Encyphering Algorithm M = Message - plain text Ke = Encryption key C = Cyphered text Decryption: M = D( C, Kd ) D = Decyphering Algorithm Kd = Decryption key 15:Security 16 Cryptography
- 17. SECURITY DEFINITIONS: Cryptosystems are either Conventional or Public Key Conventional is symmetric; Ke = Kd , so the key must be kept secret. Algorithms are simple to describe, but complex in the number of operations. Public key is asymmetric; Ke != Kd , so Ke can be made public. Kd is secret and can't easily be derived from Ke . Security against attack is either: Unconditionally secure - Ke can't be determined regardless of available computational power. Computationally secure: - calculation of Kd is economically unfeasible ( it would overwhelm all available computing facilities.) The only known unconditionally secure system in common use! Involves a random key that has the same length as the plain text to be encrypted. The key is used once and then discarded. The key is exclusively OR'd with the message to produce the cypher. Given the key and the cypher, the receiver uses the same method to reproduce the message. 15:Security 17 Cryptography
- 18. SECURITY DATA ENCRYPTION STANDARD ( DES ): The official National Institute of Standards and Technology (NIST), (formerly the National Bureau of Standards) encryption for use by Federal agencies. The source of security is the non-linear many-to-one function applied to a block of data. This function uses transposition and substitution. The algorithm is public, but the key (56 bits) is secret. Computational power today can crack a 56 bit code. In common use today is Triple DES in which 3 different keys are used, making the effective key length 168 bits. 15:Security 18Data Encryption Standard
- 19. SECURITY The general principle is this: 1. Any RECEIVER A uses an algorithm to calculate an encryption key KEa and a decryption key KDa. 2. Then the receiver PUBLICIZES KEa to anyone who cares to hear. But the receiver keeps secret the decryption key KDa. 3. User B sends a message to A by first encrypting that message using the publicized key for that receiver A, KEa. 4. Since only A knows how to decrypt the message, it's secure. 15:Security 19Public Key Cryptosystems Public Key Repository KEa KEb KEc
- 20. SECURITY To be effective, a system must satisfy the following rules: a) Given plaintext and ciphertext, the problem of determining the keys is computationally complex. b) It is easy to generate matched pairs of keys Ke, Kd that satisfy the property D( E( M, Ke ), Kd ) = M. This implies some sort of trapdoor, such that Ke and Kd can be calculated from first principles, but one can't be derived from the other. c) The encryption and decryption functions E and D are efficient and easy to use. d) Given Ke , the problem of determining Kd is computationally complex. What is computationally difficult? Problems that can't easily be calculated in a finite time. Examples include: factoring the product of two very large prime numbers; the knapsack problem. These problems are NP complete - solution times are exponential in the size of the sample. 15:Security 20Public Key Cryptosystems
- 21. SECURITY To be effective, a system must satisfy the following rules: e) For almost all messages it must be computationally unfeasible to find ciphertext key pairs that will produce the message. (In other words, an attacker is forced to discover the true (M,Ke) pair that was used to create the ciphertext C.) f) Decryption is the inverse of encryption. E( D( M, Kd ), Ke ) = D( E( M, Ke ), Kd ) 15:Security 21Public Key Cryptosystems
- 22. SECURITY AN EXAMPLE: 1. Two large prime numbers p and q are selected using some efficient test for primality. These numbers are secret: 2. The product n = p * q is computed. 3. The number Kd > max( p, q ) is picked at random from the set of integers that are relatively prime to and less than L(n) = ( p - 1 ) ( q - 1). 4. The integer Ke , 0 < Ke < L(n) is computed from L(n) and Kd such that Ke * Kd = 1 (mod L(n)). 15:Security 22Public Key Cryptosystems Let p = 3, q = 11 n = 3 * 11 = 33. L(n) = ( p - 1 ) ( q - 1 ) = 20. Choose Kd > 11 and prime to 20. Choose Kd = 13. 0 < Ke < 20 Ke = 17. (since 17 * 13 = 221 = 1 ( mod 20 ) )
- 23. SECURITY AN EXAMPLE: Separate the text to be encoded into chunks with values 0 - ( n - 1 ). 15:Security 23Public Key Cryptosystems In our example, we'll use < space = 0, A = 1, B = 2, C = 3, D = 4, E = 5 >. Then " B A D <sp> B E E " --> "21 04 00 25 05" 21 ^ 17 ( mod 33 ) = 21. 21 ^ 13 ( mod 33 ) = 21. 04 ^ 17 ( mod 33 ) = 16. 16 ^ 13 ( mod 33 ) = 04. 00 ^ 17 ( mod 33 ) = 00. 00 ^ 13 ( mod 33 ) = 00. 25 ^ 17 ( mod 33 ) = 31. 31 ^ 13 ( mod 33 ) = 25. 05 ^ 17 ( mod 33 ) = 14. 14 ^ 13 ( mod 33 ) = 05. This whole operation works because, though n and Ke are known, p and q are not public. Thus Kd is hard to guess. [Note: recently a 100 digit number was successfully factored into two prime numbers.]
- 24. SECURITY AUTHENTICATION AND DIGITAL SIGNATURES: Sender Authentication: In a public key system, how does the receiver know who sent a message (since the receiver's encryption key is public)? Suppose A sends message M to B: a) A DECRYPTS M using A's Kd(A ) . b) A attaches its identification to the message. c) A ENCRYPTS the entire message using B's encryption, Ke(B) C = E ( ( A, D( M, Kd(A) ) ), Ke(B) ) d) B decrypts using its private key Kd(A) to produce the pair A, D( M, Kd(A) ). e) Since the proclaimed sender is A, B knows to use the public encryption key Ke(A). Capture/Replay In this case, a third party could capture / replay a message. The solution is to use a rapidly changing value such as time or a sequence number as part of the message. 15:Security 24 Public Key Cryptosystems
- 25. SECURITY Man-in-the-middle Attack on Asymmetric Cryptography 15:Security 25 Public Key Cryptosystems Sender Receiver Here are the attack steps for this scenario: 1.Sender wishes to send a message to Receiver. 2.S asks R for its encryption key. 3.When R returns key, that key is intercepted by the attacker who substitutes her key. 4.Sender encrypts message using this bogus key and returns it. 5.Since the attacker is the owner of this bogus key, the attacker can read the message.
- 26. SECURITY Insertion of cryptography at one layer of the ISO network model (the transport layer) SSL – Secure Socket Layer (also called TLS) Cryptographic protocol that limits two computers to only exchange messages with each other Very complicated, with many variations Used between web servers and browsers for secure communication (credit card numbers) The server is verified with a certificate assuring client is talking to correct server Asymmetric cryptography used to establish a secure session key (symmetric encryption) for bulk of communication during session Communication between each computer uses symmetric key cryptography 15:Security 26 Example - SSL
- 27. SECURITY Security is based on user accounts Each user has unique security ID Login to ID creates security access token Includes security ID for user, for user’s groups, and special privileges Every process gets copy of token System checks token to determine if access allowed or denied Uses a subject model to ensure access security. A subject tracks and manages permissions for each program that a user runs Each object in Windows XP has a security attribute defined by a security descriptor For example, a file has a security descriptor that indicates the access permissions for all users 15:Security 27 Example – Windows 7
- 28. SECURITY U.S. Department of Defense outlines four divisions of computer security: A, B, C, and D. D – Minimal security. C – Provides discretionary protection through auditing. Divided into C1 and C2. C1 identifies cooperating users with the same level of protection. C2 allows user-level access control. B – All the properties of C, however each object may have unique sensitivity labels. Divided into B1, B2, and B3. A – Uses formal design and verification techniques to ensure security. 15:Security 28 Security Classifications