Networking Basics for Hackers, Part 2 in the first a part of this collection, I introduced you to the basics of networking such as IP addresses.

​To come to be a proficient hacker, forensic investigator Networking Basics for Hackers, Part 2:

ports, NAT, and DHCP. in this lesson, I need to introduce you to the fundamentals of TCP/IP, i.e., Transmission control Protocol (TCP) and internet Protocol (IP). those are the maximum commonplace protocols used on the net for verbal exchange Networking Basics for Hackers, Part 2.

or in reality be an awesome community engineer, you need to understand the shape and anatomy of those protocols. From my experience, many professionals in those fields do not recognize the fundamentals of TCP/IP, this means that that you may really have an advantage over them in case you do apprehend TCP/IP.

​whilst looking to create a new hacking tool or look into a network assault, information these protocols and their fields is important. otherwise, you’ll be actually wasting your time.

​What Are Protocols?

Protocols are absolutely an agreed upon manner to communicate. as an example, we here on Hackers-rise up have agreed upon the English language with all its rules and grammar as our way to talk. this is our protocol. If we did now not have an agreed upon manner to talk, human beings could be the usage of many languages, grammar, and rules and none of us could apprehend each different Networking Basics for Hackers, Part 2.

​Protocols are comparable. A protocol simply defines a way of verbal exchange with all its rules. these guidelines are typically defined by a RFC (Request for comments).

​there are numerous, many protocols in use at the internet. those include TCP, IP, UDP, FTP, HTTP, SMTP, and many others., and each has its very own set of policies that should be complied with that allows you to communicate efficiently (much like the policies we use in conversation via written languages). probably the 2 most critical protocols for use over the net are IP and TCP, so allow’s check every of those Networking Basics for Hackers, Part 2.

​IP (internet Protocol)
​
IP, or net Protocol, is the protocol this is used to define the supply and destination IP cope with of a packet as it traverses the net. it is regularly used together with different protocols which include TCP, for this reason the frequently used conjunction, TCP/IP.

​let’s check an IP packet header and notice what records it carries that can be beneficial to the aspiring hacker and/or forensic investigator.

​​Row 1

​model: This defines the version of IP, either v4 or v6.

IHL: Defines the header length.

kind of provider (TOS): This defines the form of provider of this packet. those consist of decrease delay, maximize throughput, maximize reliability, and limit economic value.

total period: This defines the total period of the IP datagram (including the information) or the fragment. Its most price is sixty five,535 Networking Basics for Hackers, Part 2.

​Row 2

​identification: This discipline uniquely identifies every packet. it is able to be critical in reassembling fragmented packets.

IP Flags: This area defines whether the packet is fragmented (M) or no longer (D). The manipulation of the field may be used to avoid IDS and firewalls. check out my tutorials on nmap and hping3 on how we can control packets to avoid intrusion detection structures and different safety gadgets. it is able to also be used along side the Window subject to pick out the operating machine of the sender.

Fragment Offset: This area is used while packets are fragmented. It defines in which the packets must be reassembled from the start of the IP header Networking Basics for Hackers, Part 2.

​Row 3

​TTL: that is the “time to live.” This defines what number of hops across the net earlier than the packet expires. It varies by running system making it useful to perceive the OS of the sender.

Protocol: This area defines what protocol is getting used with IP. most often, it’ll be 6 or TCP, 1 for ICMP, 17 for UDP, amongst others.

Header Checksum: this is an error checking discipline. It calculates the checksum (a easy set of rules) to decide the integrity of the data in the header Networking Basics for Hackers, Part 2.

​Rows4 & five

​source / destination: those rows of the IP header are in all likelihood the most essential a part of the header because it contains the source and vacation spot IP deal with.

alternatives: This area is variable length and its use is optionally available (as you would possibly assume).

Padding: This area is used to fill out, if vital, the ultimate bits and bytes of the header Networking Basics for Hackers, Part 2.

​TCP (Transmission control Protocol)
​
inside the TCP header, there are various essential fields that the aspiring hacker and/or forensic investigator ought to apprehend.

​supply Port / vacation spot Port: probable most importantly, those are the source port and destination port. these fields determine what port the verbal exchange got here from (supply) and in which it’s far going (vacation spot).

​series range: The series quantity is generated by the supply gadget’s TCP stack and is used to ensure that packets are organized in the proper sequence whilst they come. it’s also critical in defeating MitM assaults Networking Basics for Hackers, Part 2.

​Row 3

​Acknowledgement range: this is an echo of the series number sent lower back by using the receiving gadget. It basically says, “I received the packet with the series #.” in this way, the sender is aware of that the packet arrived. If the sender does no longer receive an Acknowledgment number back in a set quantity of time, it’ll resend the packet to make certain the receiver receives the packet. in this manner, TCP is dependable (in contrast, UDP does not do this and is therefore unreliable Networking Basics for Hackers, Part 2).

​Row four

​The fourth row has a few vital records. allow’s skip over the statistics Offset and the Reserved fields. That takes us to eight bits close to the center of Row 4. those are the infamous flags of the three-way handshake and Nmap scans.

the first bits, CWR and ECE, are beyond the scope of this lesson. the next six bits are the URG, ACK, PSH, RST, SYN, and FIN flags. these flags are utilized by TCP to talk;

​SYN: the hole of a new connection.

FIN: The ordinary, “soft” remaining of a connection.

ACK: The acknowledgment of a packet. All packets after the 3-way handshake should have this bit set.

RST: The tough-close of a connection and commonly used to communicate that the packet has arrived at the incorrect port or IP.

URG: This flag indicates that the following facts is pressing.

PSH: Push the facts past the buffer to the application Networking Basics for Hackers, Part 2.

​if you are familiar with Nmap or Hping3 as recon equipment, you’ve got used scans utilizing all of these flags. through creating packets with flag mixtures that need to not be visible inside the wild, we can be capable of elicit a response from a completely comfortable gadget or even avoid detection.

​Window size: In some diagrams, that is definitely defined as the Window area. it’s role is to communicate the dimensions of the window that the TCP stack has to buffer packets. that is the way that TCP manages glide manage. From a recon or forensics attitude, this discipline by myself may be enough to discover the OS that despatched the packet. This area varies from OS to OS and even from SP to SP Networking Basics for Hackers, Part 2.

Given this little bit of data, you possibly can predict with about eighty% accuracy the OS that despatched the packet. In truth, it’s far this discipline and some others (DF and TTL in the IP header) that such operating device fingerprinters inclusive of p0f use to become aware of the OS Networking Basics for Hackers, Part 2.

​Row five

​Checksum: This field uses a simple algorithm to check for errors. In essence, it’s far an integrity checker.

URG Pointer: This area factors to the closing byte of the series variety of pressing information. The URG flag must be set in conjunction to spark off this subject.

​​alternatives: just like the IP header, the TCP header has an options area that may be used if necessary and it’s far varying length Networking Basics for Hackers, Part 2.

Padding: The padding is essential to convey the TCP header to a more than one of 32 bits.

​if you have any questions about these basics of TCP/IP, ask within the comments under and we will try and assist you understand better.

​hold coming back, my greenhorn hackers, as we explore the fundamentals of networking to make you a expert hacker Networking Basics for Hackers, Part 2!

​also, search for my upcoming e-book “network basics for Hackers”.

A community is a collection of two or extra devices which might be connected to every other to proportion the facts or share the useful resource. A network contains some of one-of-a-kind computer device this is linked via a physical or wireless connection like server or router. This router has direct get right of entry to to the net. The tool can best connect to the internet via the router or get right of entry to factor.

for instance: suppose the patron or device connected to the network thru wireless or Ethernet. If the client opens the browser and brands google.com, then your pc will send a request to the router for asking google.com. The router will go to the net and request google.com. The router will acquire google.com and ahead that response to the laptop. Now the purchaser can see google.com at the browser as a result Networking Basics for Hackers, Part 2.

primary of network

In networking, devices at the identical community communicate with every other the use of packets. if you ship a video, login a website, sending chat messages, sending e mail, all of the records is ship as packets. In networking, devices ensure that these packets go within the right path using the mac address. each packet has the source mac and vacation spot mac, and it flows from the supply mac to vacation spot mac.

if you’re getting started along the thrilling path of hacking, cybersecurity, and pentesting, Linux fundamentals for Hackers is an awesome first step. the usage of Kali Linux, an advanced penetration trying out distribution of Linux, you will study the fundamentals of using the Linux working system and collect the tools and techniques you will need to take control of a Linux surroundings Networking Basics for Hackers, Part 2.

First, you’ll learn how to deploy Kali on a virtual system and get an creation to fundamental Linux ideas. next, you’ll address broader Linux topics like manipulating textual content, controlling document and listing permissions, and coping with consumer surroundings variables. you may then attention in on foundational hacking principles like security and anonymity and examine scripting abilties with bash and Python. practical tutorials and sports during will beef up and take a look at your skills as you learn how to Networking Basics for Hackers, Part 2:

– cover your tracks with the aid of changing your network data and manipulating the rsyslog logging application
– Write a device to test for community connections, and join and listen to wi-fi networks
– keep your net hobby stealthy the usage of Tor, proxy servers, VPNs, and encrypted e-mail
– Write a bash script to test open ports for potential goals
– Use and abuse offerings like MySQL, Apache internet server, and OpenSSH
– construct your very own hacking gear, together with a far flung video spy camera and a password cracker

Hacking is complex, and there may be no unmarried way in. Why not start at the start with Linux basics for Hackers Networking Basics for Hackers, Part 2?
about the author
OccupyTheWeb is an infosec representative, forensic investigator, and trainer with greater than 20 years in the enterprise. He keeps the Hackers-get up schooling web site (https://www.hackers-get up.com/) and trains US navy employees, department of defense contractors, and federal employees in statistics security and hacking.
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Sources