Revision Lecture: 6th December 2019 Flashcards Preview

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Flashcards in Revision Lecture: 6th December 2019 Deck (78)
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1
Q

What is the Chinese Wall?

A

A security model grouping commercial information into a centralised repository and basing authorisation to access information based on previous activity in order to avoid spying and conflicts of interest.

2
Q

How does the Chinese Wall perform authorisation?

A

Essentially people are authorised to access an object if they have never accessed information from a company in a shared conflict class with the company whose info is being accessed.

The ss-property means that you may only read sanitised (public) information or information from companies whose competitors’ information you have not previously accessed.

The star-property means that subjects may only write to an object if they are unable to read any objects of any other companies which have competitors.

3
Q

How does the Chinese Wall work?

A

You have a single centralised store of commercial data. Objects are files or data pertaining to one company. Groups are made of the objects, company wise (i.e. all their objects). Conflict classes are made which hold all groups for a set of competing companies, e.g. oil companies or social media companies.

Objects are labelled by their owning company and competitor companies, from conflict classes.

Essentially people are authorised to access an object if they have never accessed information from a company in a shared conflict class with the company whose info is being accessed.

Sanitised information which can be made public has no competitor company.

4
Q

What is the Clark-Wilson Framework?

A

An integrity model that seeks to allow the integrity policies of computer systems to be specified and analysed.

5
Q

How does the Clark-Wilson Framework work?

A

Have states and transitions when subjects perform actions on objects. Actions possible performed by valid and consistent end states, only being via intermediary programs, order, and user privileges based on role/job.

Transactions are groups of actions made by users on object/s. Restrictions on nobody doing two successive actions, only certain permitted order, and only being allowed to do certain actions implemented with triples: only some actions are allowed by certain subjects on certain objects.

6
Q

What are MLS systems?

A

MLS = Multilevel security = a security model in which data and users have different classifications (levels) in which users may only access objects if they have a security level classificaiton greater than or equal to that of the object

7
Q

What is security policy?

A

A set of rules and practices governing how a system
will manage and protect files with especial regard to sensitive data or code. Some companies will write a Security Policy document that defines the security (and safety) of the system. This can be considered as a legal
document if the company has an intrusion.

8
Q

What is Kerberos?

A

The distributed Access Control system which was the default option in Windows 2000. It provides authentication to users on the basis of tickets.

9
Q

How does Kerberos work?

A

The protocol for ticket granting is a variant of Needham-Schroeder:

Alice logs onto server Sam using a password and requests resource B:

  1. A ->S: A, B

The client software in her PC fetches a ticket encrypted under her password and which contains the key KAS. For access to resource B, the ticket KAB with timestamp TS and lifetime L is given.

  1. S->A: {TS, L, KAB, B, {TS, L, KAB, A}KBS }KAS

Alice gets a copy of the ticket to read encrypted under KAS. She verifies the ticket by sending the timestamp TA to B which confirms its liveness by sending back the timestamp incremented by 1.

  1. A->B: {TS, L, KAB , A}KBS , {A, TA}KAB
  2. B->A: {TA + 1}KAB
10
Q

What can and cannot Kerberos do?

A

It can’t protect against MITM attacks. It provides a ticket-based authentication mechanism using keys in a variant of the Needham–Schroeder protocol. it uses timestamps and lifetimes to try to stop key stockpiling, a problem in normal N-S.

11
Q

What is WPA2?

A

The second version of WPA (Wi-Fi Protected Access), a security protocol designed to secure connections to wireless access points.

12
Q

How does WPA2 work?

A

In WPA2 Personal mode, authentication is between the client and an Access Point (AP) with the AP generating a PSK from a plain text passphrase that is used for all devices.

In Enterprise mode, the AP provides access control to the authentication (RADIUS) server. The AP has 2 logical parts: service and authentication and Port Access Entity (PAE). The authentication PAE is always open. The service is opened after successful authentication using
EAPoL (EAP over LAN). Because each device is authenticated before it connects, a personal, encrypted tunnel is effectively created between the device and the network.

13
Q

How do WPA2 handshakes work?

A

Handshakes between user (supplicant) and WAP (authenticator) and WAP (supplicant) and router (authenticator) to make a path user -> WAP -> router.

In a 4-way handshake:

  1. Both already have PMK which is secret and never sent
  2. authenticator (A) to supplicant (S): EAPOL-KEY msg 1 with Anonce (authenticator nonce) => PTK made in S
  3. S to A: EAPOL-KEY msg 2 with Snonce (supplicant nonce) => PTK made in A
  4. GTK made in A and then sent to S in E-K msg 3 => S installs the GTK
  5. S to A: E-K msg 4 confirming temporal keys (PTK and GTK) installed in both => A installs GTK

Steps 2-4 are MIC protected

PTK = pairwise transient key = unicast
GTK = group temporal key = multicast

Each device makes PTK from its PMK and a nonce from the other device

14
Q

Why are periodic reauthentications used in WPA2?

A

Redo the authentication process every 15-20s because then an attacker would have to as well to keep eavesdropping. This would be difficult to do within that time period due to strong security and also limits data leakage to one of those periods if one ever is compromised.

15
Q

How often to periodic reauthentications happen in WPA2?

A

every 15-20 seconds

16
Q

What is SNA?

A

SNA = Social Network Analysis = the process of gathering, investigating, and assessing data from social networks and social media platforms and trying to understand them in terms of relationships.

17
Q

How do you find the monetary value of a social network?

A

From Metcalfe’s law, the monetary value of a network is directly proportional to the square of the size of the network (no of nodes in it).

18
Q

What is a hub?

A

A central node, connected to all (or many) others, as in a star computer network.

19
Q

What is the core of a network?

A

The node or nodes in the centre of a social network which has a high level of closeness, betweenness, and product of the in degree and out degree: number of inbound and outbound vertices.

20
Q

What is a clique?

A

A total (completely adjacent - connected) group of nodes on a social network graph. They will have shared views. Cliques on social media have shared views, beliefs, or opinions. Think echo chamber. Note if you can monitor one, since all connected, you can monitor them all.

21
Q

What is a cluster?

A

A collection of individuals with dense friendship patterns internally and sparse friendships externally.

22
Q

What is the difference between a cluster, group, and clique?

A

Group = a collection of multiple nodes in a social network.

Cluster = a group of individuals with dense friendship patterns internally and sparse friendships externally.

Clique = A total (completely adjacent - connected) group of nodes on a social network graph. They will have shared views. Cliques on social media have shared views, beliefs, or opinions. Think echo chamber. Note if you can monitor one, since all connected, you can monitor them all.

So a group is any selection of nodes, clusters are groups more connected inwards v out, and cliques are groups in which all nodes are connected to all the others.

23
Q

What is a triad?

A

A clique of 3 nodes.

24
Q

What is a bridge?

A

A node or nodes connected to multiple cliques or clusters and forming connections between them.

25
Q

What is a bridge endpoint?

A

Nodes which form the initial connection of a bridge which connects a clique or cluster it to one or more other cliques or clusters.

26
Q

What is degree?

A

The number of nodes a given node is connected to.

27
Q

What is closeness?

A

How “close” a node is to others. Closeness = 1 / (mean length of shortest paths from that node to all others)

28
Q

What is betweenness?

A

A representation of how often a node is a bridge: the proportion of the number of times a given node is on the shortest path or paths between each other pair of nodes other than the given node.

29
Q

What is reach?

A

The number of people who will view a social media post.

30
Q

What is distance?

A

The minimum number of the edges in the shortest path between two nodes.

31
Q

How do the degree of nodes on social networks affect the effect they would have if breached?

A

Higher degree have higher effect: can intercept/spoof messages more as connected to more other nodes.

32
Q

Why are bridge endpoints important?

A

Analysing them gives you a more representative insight into network topology and activity than looking within one clique as they are connected to multiple cliques, which have similar messages within themselves. They also are likely to be connected to more nodes so will also be able to see more activity overall than non-bridge nodes.

33
Q

What are social network boundaries?

A

The nodes forming the edge of a clique.

34
Q

How can you decide where the core of a network is?

A

One or more of:

  1. highest level of closeness
  2. highest level of betweenness
  3. highest product of the in degree and out degree: number of inbound and outbound vertices.
35
Q

What are system boundaries?

A

The edge of artificially defined subsections of computer systems made to improve security, performance, and modularity. They involve a number of assets and resources of the computer system.

36
Q

What are graphical passwords?

A

Authentication systems in which users choose from a collection of images as a search metric.

37
Q

What are loci metrics?

A

A search metric in which locations on an image are used to match and identify users.

38
Q

What were some problems with loci metrics?

A

people choose pronounced and prominent features as marker points, lowering entropy

39
Q

What were some problems with graphical passwords?

A

Visually impaired can’t use; technically difficult to verify shapes; drawings generally simple, central, and symmetric: low entropy.

40
Q

What is Passfaces?

A

An authentication system developed as part of a research project involving a 9x9 grid of people’s faces, one of which you click each time.

41
Q

What are some problems with Passfaces?

A

People choose pretty young women, other than old women, and people choose their own race, etc. Psychological factors lowering entropy.

42
Q

What are mnemonics?

A

A memory technique using sentences to remember letters. You get the letters at the start of each word and think of a sentence of words starting with each letter to remember the letters.

43
Q

How are mnemonics relevant to passwords?

A

You would generate random letters then think of words starting with each and remember the sentence in order to remember the password.

e.g. remember “refgf” as “red ewoks firing green fireworks”

44
Q

What are phonemes?

A

A distinct unit of sound that distinguishes one word from another in a language, e.g. p and b in pat and bat.

45
Q

How are phonemes relevant to passwords?

A

Can build up passwords from phonemes or words to be pronounceable to make them easier to remember.

46
Q

What are access controls?

A

Security techniques employed to restrict the usage of a resource on a computer system by its users.

47
Q

What is MAC?

A

MAC = Mandatory access control = a variant of techniques restricting the usage of computer system resources in which OSes enforce who can access resources, and their creators cannot.

48
Q

What is DAC?

A

DAC = Discretionary access control = a variant of techniques restricting the usage of computer system resources in which OSes enforce who can access resources, as well as the creators of the resource. They can use discretion to pass priveledges on to others.

49
Q

How does MAC work?

A

Security attributes (labels) that determine whether a subject can access a resource are assigned by an administrator. Subjects cannot change the security class of an object.

50
Q

How does DAC work?

A

Users that made or own resources set their own protection levels for users and groups for the system (admin or OS) to enforce. Identity-based access control is implemented in DAC since it is based on the identities of subjects.

51
Q

What are the ISO27000-series standards?

A

A family of computer security standards guiding how to assess and mitigate a broad range of risks to computer systems.

52
Q

What types of risk do the ISO27000-series standards involve?

A
  • physical: stealing
  • computational: virus, damaging code error
  • environmental: fires, floods
  • human: accidentally causing a power outage that causes data loss
53
Q

What does appendix C of the ISO27000-series standards pertain to?

A

!

54
Q

What does appendix D of the ISO27000-series standards pertain to?

A

!

55
Q

What does the Chinese Wall consist of?

A

Objects: files, low-level information pertaining to one company.

Groups: All objects pertaining to one company is grouped together.

Conflict Classes: all groups of objects for competing companies are clustered together

56
Q

Who made the Chinese Wall?

A

Brewer and Nash

57
Q

What is the Chinese Wall model aka?

A

The Brewer and Nash model

58
Q

What is the ss-property in the Chinese Wall?

A

You may only read sanitised (public) information or information from companies whose competitors’ information you have not previously accessed.

59
Q

What is the star-property (*-property) in the Chinese Wall?

A

Subjects may only write to an object if they are unable to read any objects of any other companies which have competitors.

60
Q

What does the ss-property in the Chinese Wall not guard against?

A

A tertiary company being used to pass information between subjects of companies

61
Q

What are the implications of the star-property and ss-property in the Chinese Wall?

A

You can read from multiple companies at once, as long as they are not competitors (apart from passing via third parties) due to the ss-property. But due to the star-property, you may only write to an object if you cannot read any objects of any other companies that have competitors. This means you cannot write to more than one company’s data at once, and when you do you are unable to read data of competitors (even via third parties).

62
Q

What is a transaction in the context of the Clark-Wilson framework?

A

An action or series of actions performed by a subject, via an intermediary program, on an object, that move the system from one state to another.

63
Q

What is the well-formed transaction policy in the Clark-Wilson framework?

A

The idea that system states restrict the transactions that can be made by ensuring only transitions that move the system to valid subsequent state are executed.

Objects may only be manipulated by intermediary programs. Transactions must take place in a certain order. No user can execute two transactions one after the other. Users are limited in what they can do - programs they can call. An audit trail is made. There is a certification procedure.

64
Q

What is a Clark-Wilson access triple?

A

A tuple (of 3 or more, if more than 1 object) that records the actions a subject is allowed to perform on an object.

65
Q

What is the format of Clark-Wilson access triples?

A
66
Q

Why must you check access rights at each action attempt in the Chinese Wall?

A

Need to know what a user has previously done to determine if currently requested action is permitted and as more actions are performed they become further restricted.

67
Q

What are some vulnerabilities with the web?

A

Privacy from looking at headers even if encrypted; easy to get SSL certificate; exploits and vulnerabilities in site backends; SQL and escaped JS injections from web browsers; exploits from URL parameters of GET requests, XSS, cache poisoning, etc.

68
Q

What are some vulnerabilities with email?

A

Emails have suffered from trojans, vurises, hoaxes and of course spam.

Encryption can be done through PGP (Pretty Good Privacy) or S/MIME (Secure/Mutipurpose Internet Mail Extensions) which was designed to support Internet email. Both are used for Outook, Eudora etc and allow end-to-end security.

69
Q

What are some vulnerabilities with databases?

A
  1. Access Control: restriction levels of read, write (update). Delete must be at admin level.
  2. Authentication: Pre phase of authentication needed for access.
  3. Physical DB integrity: power failures, disc failure etc should not affect the data.
  4. Logical DB integrity: The structure of the DB is preserved after data modification (no loss of fields, keys etc).
  5. Auditability: for forensic or legal reasons as well as reconstruction.
  6. Two phase update: designed to prevent problems during update (long intent phase and then commit phase when commit flag is set)
70
Q

What is substitution?

A

!

71
Q

What is transposition?

A

!

72
Q

What is Needham–Schroeder?

A

!

73
Q

How does Needham–Schroeder work?

A

!

74
Q

How does substitution work?

A

!

75
Q

How does transposition work?

A

!

76
Q

What is RBAC?

A

!

77
Q

How does RBAC work?

A

!

78
Q

How do keys work in WPA2?

A

!