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What Makes a Network Vulnerable?

What Makes a Network Vulnerable?. Anonymity Many points of attack (targets & origins) Sharing Complexity of system Unknown perimeter Unknown path. Who Attacks Networks. Hackers break into organizations from the outside Challenge Fame Money & Espionage Ideology

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What Makes a Network Vulnerable?

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  1. What Makes a Network Vulnerable? • Anonymity • Many points of attack (targets & origins) • Sharing • Complexity of system • Unknown perimeter • Unknown path

  2. Who Attacks Networks Hackers break into organizations from the outside Challenge Fame Money & Espionage Ideology However, most security breaches are internal, by employees and ex-employees

  3. Threat Precursors • Port Scan • Social Engineering • Reconnaissance • Bulletin Board / Chat • Docs • Packet Sniffers (telnet/ftp in cleartext)

  4. Network Security Threats • Interception • If interceptor cannot read, have confidentiality (privacy) • If cannot modify without detection, have message integrity

  5. Network Security Threats • Impostors (Spoofing/ Masquerade) • Claim to be someone else • Need to authenticate the sender--prove that they are who they claim to be Impostor True Person

  6. Network Security Threats • Remotely Log in as Root User • Requires cracking the root login password • Then control the machine • Read and/or steal information • Damage data (erase hard disk) • Create backdoor user account that will let them in easily later Root Login Command

  7. Security Threats • Content Threats • Application layer content may cause problems • Viruses • In many ways, most severe security problem in corporations today • Must examine application messages

  8. Replay Attack • First, attacker intercepts a message • Not difficult to do

  9. Replay Attack • Later, attacker retransmits (replays) the message to the original destination host • Does not have to be able to read a message to replay it

  10. Replay Attack • Why replay attacks? • To gain access to resources by replaying an authentication message • In a denial-of-service attack, to confuse the destination host

  11. Thwarting Replay Attacks • Put a time stamp in each message to ensure that the message is “fresh” • Do not accept a message that is too old • Place a sequence number in each message • Do not accept a duplicated message Message Time Stamp Sequence Number

  12. Thwarting Replay Attacks • In request-response applications, • Sender of request generates a nonce (random number) • Places the nonce in the request • Server places the nonce in the response • Neither party accepts duplicate nonces Request Response Nonce Nonce

  13. Network Security Threats • Denial of Service (DOS) Attacks • Overload system with a flood of messages • Or, send a single message that crashes the machine

  14. Denial of Service (DOS) Attacks • Transmission Failure • Connection Flooding • Echo-Chargen • Ping of Death • Smurf • Syn Flood • Traffic Redirection • DNS Attacks • Distributed Denial of Service

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