The Internet Flashcards
(25 cards)
Internet
Mostly a large mesh of fibre optic cables, connecting networks all over the world. But all things connect to it, though VPN, satellite, ethernet and more. Basically an extremely large and fast WAN.
Connection to the internet
LAN’s and WAN’s all connect to the internet through ISP’s(internet service providers)
Routers
Router is a device that sends packets of data, between networks. Edge routers are the routers that link one network to another, in homes, ISP’s, businesses. Core routers are the backbone of the internet, this is what ISP’s connect to.
Packet Switching
The action of sending data across the internet in small packets(so data is all sent separately), travelling from router to router until it reaches its destination. Each router will decide what the best next router to send it to based on its destination address.
Problems with packet switching.
Routers can become busy with lots of packets, it will just work through them which may cause slight delays in loading or downloading etc, but the packet will get there. Some packets have higher priority, so will be sent first. If for some reason a packet can’t get to it’s destination, it may be caught in a loop going from router to router. All packets have a time to live, after this time it will be discarded, to stop this from happening.
Firewalls
Sits between two networks, one trusted and one untrusted, to try block malicious traffic from entering, as well as stopping certain data types leaving the trusted one.
Static filtering
Firewalls use static filtering, by checking the headers of packets against a rules disallowed on the network. They are the ones it will block. It will miss any attacks where packets have been set up to appear not harmful.
Dynamic filtering
After a packet has entered, the firewall will continuously monitor each packet and all the data inside for suspicious activity using a connection table. It could then intervene and disconnect the packet if it needs to
Proxy server
Sits between the client devices and the firewall. Hides users IP’s, logs user activities, keeps it’s own cache of websites, so the user can access them quickly. Can be used to filter websites.
Encryption
A technique used to protect data, by making it unreadable if intercepted. Uses a key to decrypt encrypted data at it’s destination
Symmetric encryption
Uses the same key for encryption and decryption, they must encrypt data with the private key, then send data, and separately they must send the key, so the recipient can decrypt it. More risky as both the key and data could be intercepted.
Asymmetric encryption
Uses a pair of keys, a public and a private. To send data from one person to another, the sender needs to encrypt the message using the receivers public key (which everyone can know), then the receiver can decrypt the message with their own private key(nobody knows this). Simply, encrypt with destinations public key, send it, and they will decrypt it with their private key.
Digital signatures (used in asymmetric encryption)
A signature to verify that the data someone has received has been unchanged after the person sent it. To generate a digital signature, the sender must produce a hashed version of their message, encrypt it with their private key, attach it to the message, and encrypt the whole thing with the recipients public key like normal. When received, they will decrypt the message with their own private key, giving them the completed message and a digital signature. They will decrypt this with the senders public key, then hash the main message to see if it matches the hash of the main message the sender made. If it does, then the message hasn’t been changed.
Data certificate
A certificate, containing the serial number, expiry date, name and signature of a website or message sender, given out by a separate certification authority. Used to verify the identity of the entity, and it’s not an impersonation. Browsers will check the certificate of every sender or website to ensure they are who they say they are.
Malware
Malicious software. Used to damage, corrupt or change files, or steal data. Types include viruses, worms and trojans.
Vulnerabilities in cyber security
Human error, we can be tricked into revealing info, downloading malware, or using insecure passwords.
Unpatched or out of date software, code is often available to cyberattack unless updated to fix small errors.
Poor code quality, malware can exploit weaknesses in code.
Viruses
A form of malware, that attaches itself to other files, so it can make copies of itself and infect computer systems. Might send spam, corrupt files or steal data. Can arrive via email attachment, on removable storage devices or on a malicious website. Will remain dormant until host file is run.
Worms
Like a virus, but they don’t need a host file, can replicate and spread independently, through network features. Usually aim to use up so much of system resources, that the network is slowed down significantly. A denial of service attack.
Trojans
A piece of software that looks friendly, like a game, that actually steals data, installs further malware or opens a backdoor, to allow remote access of computers. Doesn’t replicate, has to be run to work.
Spyware
Malicious software, that you don’t know has entered your device. Includes things like key loggers. It captures data and sends it back to the creator.
Ransomware
Software that locks a computer or encrypts its files so the user cannot access any of their data. Will then demand a fee if they want access again.
Anti-malware
Aims to detect, clean, quarantine or destroy malware on your device. Can do this in many ways, including comparing your files to a database of known malware and just monitoring files for suspicious activity.
Code quality
Having high quality code, can stop malware from taking advantage of it. For example code with poor quality memory code, can have buffer overflow problems. Causes memory to get overwrite by malware.
Code reviews
Can get other programmers to review code, to spot errors or vulnerabilities before code is released. Can also do automated reviews, where a program checks for these.
