1. Figure 1-7: Eavesdropping on a Dialog
Hello
Client PC
Bob
Server
Alice
Hello
Attacker (Eve) intercepts
and reads messages

2. Figure 1-8: Encryption for Confidentiality
Encrypted
Message
“ ”
Client PC
Bob
Server
Alice
“ ”
Attacker (Eve) intercepts
but cannot read
Original
Message
“Hello”
Decrypted
Message
“Hello”

3. Figure 1-9: Impersonation and Authentication
I’m Bob
Client PC
Bob
Prove it!
(Authenticate Yourself)
Attacker
(Eve)
Server
Alice

4. Figure 1-10: Message Alteration
Dialog
Client PC
Bob
Balance =
$1,000,000
Balance = $1
Server
Alice
Balance = $1
Balance =
$1,000,000
Attacker (Eve) intercepts
and alters messages

5. Figure 1-11: Secure Dialog System
Client PC
Bob
Server
Alice
Automatically Handles
Negation of Security Options
Authentication
Encryption
Integrity
Attacker cannot
read messages, alter
messages, or impersonate

6. Figure 1-12: Network Penetration Attacks and Firewalls
Passed Packet
Attack
Packet
Internet
Firewall
Hardened
Client PC
Internet
Attacker
Hardened
Server
Dropped
Packet
Internal
Corporate
Network
Log File

7. Figure 1-13: Scanning (Probing) Attacks
I’m Here
Attack Packets to
, , etc.
Host
Internet
Attacker
Host
I’m Here
Corporate Network

8. Figure 1-14: Single-Message Break-In Attack1.
Single Break-In Packet 2.
Server
Taken Over
By Single Message
Attacker

9. Figure 1-15: Denial-of-Service (DoS) Flooding Attack
Message Flood
Server
Overloaded By
Message Flood
Attacker

10. Figure 1-16: Intrusion Detection System (IDS)1.
Suspicious
Packet
Intrusion
Detection
System (IDS)
4. Alarm
Network
Administrator
2. Suspicious
Packet Passed
Internet
Attacker
Hardened
Server
3. Log
Suspicious
Packet
Corporate Network
Log File