L2 Paging principle with a scetch
Was ist wenig wert?
Der …
Opt., FIFO, LFU, LRU Memory Management
FIFO=First in first out
LFU=Last frequently used
LRU=Last recently used
Process State Model
What kinds of communication mechanisms between process exist? Give an example for each mechanism.
Massage Based
-Processes on same Computer
Memory Based
-Virtual Adress Space
List different options to achieve mutual exclusion for critical sections
• This condition cannot be made ineffective, since the mechanisms of mutual
exclusion must exist to avoid synchronisation problems.
• However, mutual exclusion can be limited to what is absolutely necessary. (
The likelihood of a deadlock decreases)
• For example, separation between transmission of the print job and the printing
process itself via printer spooler.
Explain the term real time capable. What is the difference between hard and soft real time?
In real-time operations, every activity has a starting point and a scheduled time, at which all results must be computed.
•Hard real-time
− Deadline misses cause intolerable damage
− Example: Missed deadline with fatal consequences for a human being
− Derivation of the term “deadline”
− The objective of hard real-time systems is to avoid or report deadline misses in time.
− Timeliness: The recipient of the alert has sufficient time to solve the problem.
• Soft real-time
− If the deadline of a task is missed, a penalty will be applied.
− The objective of soft real-time systems is to minimize the penalty sum.
Which requierments must hold for a real time system to be plannable ?
Total storage amount in bytes and number of blocks
N(number of blocks)=C(tracks)xH(heads)xS(sections)
2 Heads per disk
Bytes = Bytes per Block * N
Logical Block number of CHS Adress (c,h,s)
Give (c,h,s)-address to a locical block
LFU, LRU, FIFO
Last Frequently Used(römische Zahlen): was am wenigsten benutzt wird, wird ersetzt
Last Recently Used(hoch und runter zählen): was am ältesten ist wird ersetzt
Firs in First out(von oben nach unten): es wird periodisch von oben nach unten ersetzt
Why is using the ISO/OSImodel helpful/necessary?
The most important building block of the ISO/ OSI reference model are its seven layers.
These seven layers divide the fundamental tasks a computer network has to perform into
seven groups. For each layer services and protocols are defined.
In the context of the ISO/OSI model what is the difference between a protocol and a service?
Service:
-Interface description between layers
-group of functions
-often called primitives
-E.g. transmit x Bit to a remote station
-no specification on how to do it
Protocol:
-operational sequence description/ rules
-specifies when which kind of information has to be transmitted
-often a Finite State Machine (FSM)
-depends on the available service
Name and describe the differences between the connection types provided by the Transport Layer. Please answer the question purely theoretically and do not explain the TCP/IP example. Also provide one advantage of each connection type.
Secure Networks lecture notes 5 page 8 - 10 for pictures and informations
Tree: Typical Binary Tree. One node has nor or many children
Advantage: one way from one node to any other node
Ring: old network topology in ring structure. It sends information in one directly only or in both directions.
Advantage: redundancy when transmission in both directions supported
Mesh: very modern with a lot of destinations, can be 2D or 3D
Advantage: no bottlenecks because of redundancy
Crossbar: used in ICs or Systems on Chips
Advantage: direct and fast connection between nodes
Under which circumstances can you exchange the implement action of one ISO/OSI layer?
Performance Optimization
Compatibility
Customization
Security Enhancements
Protocol Evolution
Fault Tolerance
Resource Constraints
What is the difference between Cybersecurity and IT-Security ?
Cybersecurity:
Security within Cyberspace
Continuous process, not a static state
Defense against Cybercrime, Cybervandalism, Cyberterrorism, and Cyberwar
Partitioned into defensive and offensive security
Includes IT-Security as a large part
IT-Security:
Defense of Information Technology against negative activities in cyberspace
Focuses on protecting IT-Systems connected by the Internet
Includes measures against Cybercrime, Cybervandalism, Cyberterrorism, and Cyberwar
Subset of Cybersecurity
Describe one example of a virtual activity influencing the physical world
• Selling bitcoins transfers physical money to the sellers bank account.
• Offenses in social networks may lead to psychological injuries.
• Posting false information about a person may reduce the persons’ credibility.
• Working as an influencer transfers money to the influencers bank account.
Describe one example of a physical activity influencing
• Buying bitcoin removes physical money from the buyers bank account and transfers bitcoins to the users’ wallet.
• A power outage renders the virtual world inaccessible.
• Production downtime reduces amount of goods for selling in Cyberspace.
Which are the maion security fundamentals?
Explain them briefly!
Confidentiality: Only authorized users get access to information, data, and
messages
Integrity: non-authorized changes to information, data, and messages are recognizable
Availability: Services are always available
What is APT? Full expression!
Advanced Persistent Threat (APT)
complex attack pattern
small and large attacks
long period of time
professionally prepared
executed to stay
nation state actors
large/ professional hacker groups
In which classes can you organize threats?
Software
Hardware
Pattern
Social Engineering
Structure
Explain briefly what DNS is and how data is stored in this System
Domain Name Service is like the internet's phone book, translating domain names (like example.com) into IP addresses that computers understand.
Stored in dedicated Servers for Translation:
Root Nameserver
TLD Server operated regional registrie (Germany: DeNIC)
Nameserver from companys (Google or HSU)
Name one attackvector, threat or voulnerability in SCN and explain briefly
Rootkit
running hidden on system
actively hides itself
provides root or admin access (remote)
Ways to report volnerabilities in software or services. Explain breifly and give advantages/disadvantages
Bug Bounty Programs:
Programs where a team will actively search for volnerabilities
Advantages:
Encourages responsible disclosure and collaboration.
Disadvantages:
Limited to programs offered by specific companies.
Open-Source Projects:
Projects where everything is open to public and everyone can submit improvements
Transparent process for reporting vulnerabilities in community-driven projects.
Lack of dedicated resources for handling security reports in smaller projects.
How to improve security on the shown network. Explain briefly
Network Segmentation
Categorize your network into device Groups
Everytime the firewall controls access between these networks
Different Operating Systems
There wont be one big platform used by everyone, which makes it harder to attack all of them
Backupserver
it is a backup for your system
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