2. What is network security?
• Network security is preventing attackers from achieving
objectives through unauthorized access or unauthorized
use of computers and networks.
Basic Security Measures
• The basic security measures for computer systems fall
into four categories:
• External security:- Protection from environmental
damage.
• Surveillance:- Proper placement of security cameras can
deter theft
• Auditing:- Creating a computer or paper audit can help
detect wrongdoing
• Viruses/worms:- Many different types of viruses, such as
parasitic, boot sector, stealth, polymorphic, and macro.
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3. What is a firewall?
• Used to control the flow of traffic (both inflows
and outflows, but primarily inflows) between
networks
• The connected networks can be internal or a
combination of internal and external networks
Firewalls
A system or combination of systems that
supports an access control policy between two
networks.
A firewall can limit the types of transactions
that enter a system, as well as the types of
transactions that leave a system. 3
4. Characteristics of Good Firewalls
• All traffic from inside the •Only authorized traffic, as
corporate network to outside defined by the security policy, is
the network, and vice-versa, allowed to pass through it; and
must pass through it; the system itself is immune to
penetration.
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5. Firewalls – 2 types
A packet filter firewall is essentially a router that has been
programmed to filter out or allow to pass certain IP addresses
or TCP port numbers.
A proxy server is a more advanced firewall that acts as a
doorman into a corporate network. Any external transaction
that request something from the corporate network must enter
through the proxy server.
Proxy servers are more advanced but make external accesses
slower.
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6. Components of Firewalls
• Chokes - limit the flow of packets between
networks. Read packets and determine,
based on the rules, if the traffic should pass
• Gates - act as a control point for external
connections. They control the external
connections.
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7. TELNET FTP SMTP SMTP
T TP
H
SM
TP
TP
SM
FT
TP
P
F
FT
TP PACKETS
P
F
SM
ET
TP
E LN
TE
Rejected Packets T
LN
TP
ET
SMTP HTTP SMTP T
H
CHOKE
GATE
DEFAULT
DENY
FTP FTP TELNET
Application Level Corporate
Filtering Rule - Internal
Deny everything except Network
Telnet & FTP
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9. Hence we conclude that NETWORK SECURITY
prevents attackers from achieving the objectives through
unauthorized access…….
Firewall is very useful to provide the security in
NETWORKING.
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