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os security intro Flashcards

1
Q

what is os security

A

measures and mechanisms implemented to protect the os from threats vulnerabilities and unauthorised access

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2
Q

what is access control

A

controlling the resources that a user can access based on authentication and authorization

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3
Q

authentication

A

verifying the identity of a user

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4
Q

authorization

A

granting and restricting access based on the users roles and permissions

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5
Q

what is the active entity

A

the subject
user/process

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6
Q

what is the passive entitiy

A

the object
the file/resource

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7
Q

discretionary access control

A

the owner of the resource decided who is allowed access

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8
Q

mandatory access control

A

a system-wide policy decides who is allowed access

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9
Q

what are user identifiers

A

unique numbers assigned to users to identify and manage their access

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10
Q

what are the five types of user identifiers

A

user id uid
group id gid
effective uid euid
real uid ruid
saved uid suid

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11
Q

uid

A

assigned to each user

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12
Q

what is the uid of the root and why is this special

A

0
gives unrestricted access to the system

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13
Q

gid

A

assigned to a group of users

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14
Q

what are two benefits of gid

A

more effective as you dont need to configure permissions for each user
easier to modify permissions for the group rather than each user separately

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15
Q

euid

A

determines permissions for processes

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16
Q

ruid

A

the uid of the user who started the process

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17
Q

suid

A

allows a process to switch back to privileged uid after temporarily dropping privileges

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18
Q

nobody uid

A

massive number
used for running untrusted processes so it has minimal priveleges

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19
Q

how does assigning uid work

A

when a user logs in the system designs their uid and guid and all the files and processes created by them have the same uid and gid
when they attempt to access a resource the permissions are checked against their uid and gid

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20
Q

what are two of the potential threats with access control

A

privilege escalation
uid reuse

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21
Q

how is uid reuse a potential threat in access control

A

reassigning the uid to a new user may mean that they still have the same privileges of the old user

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22
Q

how is privilege escalation a potential threat in access control

A

hackers can exploit a misconfigured uid to gain privileges

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23
Q

what is file system security

A

protecting files and directories via permissions and encrypting sensitive data to avoid unauthorised access

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24
Q

what are the three parts of file permissions (+ explain them)

A

ownership: all owned by a specific user/group that decide the permissions
permission types (r, w, x)
levels: user(owner) , group, others

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25
which two apps can we use to check the integrity of a file and what exactly do they do
tripwire aid checks for unauthorised access
26
what is the concept of least privilege
is privileges are appropriate they'll allows processes and users to have the least privileges required to carry out their tasks
27
what are the uid 1-999 reserved for
for system services and daemons
28
how does file permissions work in linux
rwx stored together for user, group and others with - if they dont have that permission e.g. rwxr-----
29
process isolation
ensures that each process has its own space so they dont interfere with each other and access/ corrupt each others memory
30
what is an example of process isolation
windows container
31
memory protection
ensures that a process only accesses authorised memory regions prevents unauthorised access to the kernel and other memory regions
32
how do privilege levels work in process and memory protection
separate user and kernel space the user has limited access whilst the kernel has access to all software hardware and memory resources
33
what are the three potential threats in process and memory protection
denial of service privilege escalation buffer overflow
34
how do we mitigate privilege escalation in process and memory protection
strict separation between user and kernel mode
35
how do we mitigate dos in process and memory protection
resource limits and process scheduling
36
what is a buffer
a contiguous memory block that stores data temporarily
37
how do attackers use buffer overflows to their benefit
overwriting memory via exploiting poorly written code to execute malicious code
38
what can an attacker do with a buffer overflow
add an account control the app remotely alter the system configuration force the program to execute commands to the cmd shell
39
what are the three types of messages with buffer overflows
bus error segmentation error general protection fault
40
segmentation error + general protection fault
memory protection deny access: usually means that theres a buffer overflow
41
bus error
memory doesnt exist
42
what are some good practices for memory and process protection
secure coding to avoid buffer overflows enabling security features regular software updates limit privileges monitor and audit
43
what are some security features that can be enabled in memory and process protection
alsr: address space layout randomisation nx: non-executable
44
alsr: address space layout randomisation
random memory allocation to attackers dont know where the buffers are
45
nx: non-executable
protected areas
46
patch management
applying security patches(updates) regularly and updating the os to fix vulnerabilities and bugs
47
what are the four types of patches
security bug fixes feature update performance patches
48
security patches
fix vulnerabilities that could be exploited by hackers
49
big fixes (patches)
resolve bugs causing crashes and errors
50
feature updates (patches)
new functionality/ improve existing features
51
performance patches
optimise os usage and increase software performance
52
what are the four types of audits
security compliance operational forensic
53
security audit
evaluate the effectiveness of security control and identify vulnerabilities
54
compliance audit
ensure adherence to regulated requirements
55
operational audit
assess efficiency and effectiveness of operational processes
56
forensic audit
investigate security incidents/breaches to determine the cause and impact
57
what are the five types of logs
system application security network audit
58
system log
record system events e.g. shutdown
59
application logs
track events within specific apps e.g. login attempts
60
security logs
security related events e.g. authentication
61
network logs
monitor the network for traffic and connections
62
audit logs
track user activities for accountability
63
what are the best practices for auditing and logging
enable comprehensive logging centralise log management protect logs regularly review logs retain logs conduct regular audits
64
what do we mean by enable comprehensive logging
ensure all critical components generate logs and are logging relevant details e.g. timestamps, uid pid
65
how do we centralise log management
collect and analyse logs from multiple sources
66
how do we protect logs
encrypt and restrict access to logs user write-once storage to prevent tampering
67
why and how do we regularly review logs
to detect anomalies via automated tools
68
how do we retain logs
should keep them for a time period as defined by policies and regulations they should be archived for future reference
69
why do we conduct regular audits
we can use audit trails to investigate incidents and track changes
70
auditing
reviewing and analysing logs and records to detect anomalies
71
logging
recording events and activities in the system/app/network
72
what are the 6 key components of patch management
inventory and assessment vulnerability monitoring patch acquisition testing deployment (deploy after testing) verification and documentation
73
inventory and assessment (patch management)
maintaining an inventory of hardware and software identify which applications require patches
74
vulnerability monitoring (patch management)
using vulnerability scanners to find new vulnerabilities and patches
75
patch acquisition (patch management)
downloading patches from trusted sources and verifying their integrity via checksums/digital signatures
76
testing (patch management)
testing patches in a controlled environment and checking for compatibility with the system/apps usually dont by the company deploying them
77
verification and documentation (patch management)
check theyre successfully applied and functioning correctly monitoring for issues maintain records of patching activities - which ones have been applied where and when

secure cyber systems (9 decks)

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