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CS426 > Final Exam (V.2) > Flashcards

Final Exam (V.2) Flashcards

1
Q

What are firewalls?

A

Provide central “choke point” for all traffic entering and exiting the system

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2
Q

Main goals of firewall?

A
  • Service control
  • Behavior control
  • User/machine control
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3
Q

Firewalls can also run security functionality, like IPsec and VPN. T/F

A

True

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4
Q

What can’t firewalls protect against?

A
  • insider attacks
  • users bypassing the firewall to connect to the Internet
  • Infected devices connecting to network internally
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5
Q

Why not just provision each computer with its own firewall/IDS?

A
  • Not cost effective
  • Different OS’s make management difficult
  • Patches must be propagated to all machines in the system
  • Does not protect against insider attacks that extend beyond the local network
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6
Q

What is default policy?

A

Specifies what to do if no other policy applies.

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7
Q

What is default deny?

A
  • blocklist/denylist
  • specifies connectivity that is explicitly disallowed
  • less secure, but allows functionality
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8
Q

What is default accept?

A
  • allowlist
  • specifies connectivity that is explicitly allowed
  • more secure but may break functionality
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9
Q

In firewall rule order, firewall policies are monotonic. T/F

A

False

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10
Q

In firewall rule order, policy evaluate by first match, not best match. T/F

A

True

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11
Q

How to optimize firewall performance?

A

Do frequent deny first

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12
Q

Stateless packets are _____ while stateful packets ____.

A

considered in isolation; allow historical context consideration

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13
Q

Advantages and disadvantages of stateless packets?

A

A: much faster packets processing
D: more complex rule specification, less secure

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14
Q

Advantages and disadvantages of stateful packets?

A

A: more simple rule specification, more secure
D: slower packets processing

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15
Q

We can have multiple network firewalls, each providing different protection. T/F

A

T

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16
Q

Multiple firewalls means they have ____ filtering rules to ________.

A

stricter; protect each server from each other

17
Q

What is a DMZ?

A

A logical subnetwork that contains and exposes an organization’s external-facing services to an untrusted, usually larger network

18
Q

In DMZ, internal network is ___ whereas the DMZ is ____.

A

trusted; semi-trusted

19
Q

DMZ hosts often communicate with both the ___ and the ___.

A

Internet; LAN

20
Q

What are honeypots?

A

Decoy systems to lure potential attackers.

21
Q

Goals of honeypots are:-

A
  • divert attackers from critical systems
  • collect information about attacker’s activity
  • delay attacker long enough to respond
22
Q

What are some features of honeypots deployed outside firewall?

A
  • can detect attempted connections to unused IP addresses, port scanning
  • no risk of compromised systems behind firewalls
  • does not divert internal attackers
23
Q

What is PKI?

A
  • a set of roles, policies, hardware, software and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption
24
Q

What are the 3 entities form a PKI?

A
  • client (connect securely or verify an entity)
  • server (prove its entity)
  • CA (validate identifies and generate certificates)
25
Q

How to obtain the signature for X.509?

A

Compute a message digest of the above fields with a hashing algorithm and then encrypting it with the CA’s private key

26
Q

What are the steps of verifying the digital certificate?

A
  • the server has a digital certificate
  • client asks for the server’s digital certificate
  • client is able to verify the server through issuing CA
27
Q

Root CA may delegate the trust to other CA’s who in turn may be allowed to delegate that trust. T/F

A

True

28
Q

The initial list of trusted Root CA’s decided on by web browser’s producer. T/F

A

True

29
Q

Any certificate signed by one of these Root CAs is trusted. T/F

A

True

30
Q

Reasons to revoke a certificate?

A
  • private key corresponding to the certified public key has been compromised
  • user stopped paying his certification fee to the CA and the CA no longer wishes to certify him
  • CA’s certificate has been compromised
31
Q

Expiration is not a form of revocation. T/F

A

False

32
Q

Because certificate serial numbers must be unique with each CA, this is enough to identify the certificate. T/F

A

True

33
Q

What is a certificate revocation list (CRL)?

A
  • CA periodically issues a signed list of revoked certificates
  • can issue a “delta CRL” containing only updates
34
Q

What is OCSP?

A
  • Online Certificate Status Protocol
  • when a certificate is presented, recipient goes to a special online service to verify whether it is still valid
35
Q

How does OCSP Stapling?

A
  • the web server sends regular, automatic OCSP requests to the OCSP responder (CA)
  • the OCSP responder provides time-stamped data
  • the web server caches this timestamped response
  • the web server sends the cached, CA-signed and timestamped data to the client. The client trusts this response because it’s digitally signed and timestamped

CS426 (8 decks)

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