Transmission Control Protocol (TCP) is a transport layer protocol that provides a connection-oriented data stream service with guaranteed, in-order delivery.

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OSCP(Offensive Security's PWK) Requirements - Specific questions =)

I wanted to ask a few questions, mainly referred to those who completed OSCP / know about it. I want to take the course, I know that understanding of TCP/IP, IP subnetting and addressing and routing ...
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2answers
383 views

What's the advantage of sending an RST packet after getting a response in a SYN scan?

I'm reading about nmap's SYN scan, and it says Nmap sends an RST immediately after the server tries to establish the handshake. My question is - why bother with the RST? Is it to prevent the server ...
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0answers
55 views

Why would I need to check data integrity after sending file over ftp, sftp or ftps? [migrated]

I need to transfer some files from remote computer and I plan to do it via FTP (or SFTP or FTPS). Apparently, FTP is based on TCP protocol and if I remember well my lessons the difference between TCP ...
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2answers
65 views

Do I have a IP leak if I use Tor and Skype/UDP?

I configure my OS so that it sends all traffic over the Tor (assume that, I configure Tor like proxy). I use Tor (which does not support UDP) and Skype (which uses UDP). My questions are: Does ...
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0answers
38 views

Replaying client hello from previous session

I am testing an SSL server. I need to capture the client hello and then replay the same client hello with the exact same field values. Here are the steps that I performed: Captured the client hello ...
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4answers
96 views

Is it possible to send HTTP packet via spoofed IP?

I have the following PHP code that writes accepted to a file named text.txt only if the IP is equal to 127.0.0.1 (loopback). If the IP doesn't match it writes denied. <?php $file = fopen('text.txt'...
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1answer
63 views

How can a server prove authenticity

I am working on a secure messaging platform and am having trouble figuring out how to protect against MITM attacks. My current setup can be summed up as follows: The server keeps a private key and ...
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3answers
92 views

Fingerprinting users based on IP addresses

Is your local IP address used to better "fingerprint" a specific user? As far as I understood TCP connections, your local IP is send to the remote server in IP packets. It could add to the overall ...
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2answers
79 views

IP leakage on Skype through VPN

Does anyone know how the traffic behaves if you configure a VPN natively through SSTP (WIN or MAC)? Because most applications use the TCP, but Skype uses UDP. I try to formulate more specific ...
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1answer
56 views

How does PeerBlock generate range descriptions?

How does PeerBlock generate the range that it displays? I thought it was through some DNS lookup, but when I do the lookup I get LeaseWeb Content Delivery Network for the attached screenshot. Instead ...
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1answer
83 views

Strange responses from an unfamiliar HTTP server

I noticed an unfamiliar device when scanning my local wireless network. It had two open (listening?) TCP ports; TCP/80 (http?) & TCP/443 (https?). In an effort to identify the unfamiliar device;...
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2answers
50 views

What is this weird localhost IP traffic on multiple ports in the 5400-5600 range?

I am encountering an issue I recently have seen in my Fedora 23 machine (latest updates). I am getting about 130 IP packets passed back and forth over the lo interface in one go, every 1 second (like ...
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1answer
63 views

OS fingerprinting via TCP

I have searched online about this topic and the only information I got is that TCP SYN/ACK can be used to know the type of the target OS. If that is true, I don't understand how this occurs? Does TCP ...
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1answer
28 views

How can you spoof a TCP connection to a device that uses the same initial sequence number for each run of a TCP handshake?

So supposing the TCP implementation on a device always uses the same initial sequence number how could you as an off path attacker exploit this to spoof a connection to this device? So in order to do ...
8
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3answers
117 views

Can a TCP connection be terminated by an attacker if SSL/TLS has been used to protect data in the TCP segment?

I understand that SSL/TLS is built on top of TCP. That is after a TCP connection is established, an SSL handshake can be started. When it is completed, all communication will be encrypted and ...
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3answers
168 views

Why is UDP port scanning slower than TCP port scanning?

I can't seem to find an answer for this. Any suggestions?
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0answers
43 views

Inconsistent duplicate TCP packets

How often does it happen that we benignly see a TCP packet that is retransmitted but has a different payload the second time? In other words, how often is it that we see a TCP packet with sequence ...
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0answers
81 views

Mitm Proxy using c# SslStream issues when doing directly from host file [closed]

Im trying to create a local windows MITM proxy with C# to deal with a now unsupported application from a company that no longer exists. The Proxy has to only service one HTTPS domain which is being ...
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0answers
124 views

Is this c# digital signature implementation secure?

The code connects multiple clients to a server using TCP sockets asynchronously. I have added code to attach a digital signature to the outgoing messages from the server, to authenticate the message ...
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2answers
160 views

Beginner > Medium > Advanced Books/Guides/Tutorials on TCP/IP [closed]

Long time web developer looking to get into infosec. Was hoping on guidance on material from a beginners stance on TCP/IP and hopefully "networks". I realise the massive generalisation I'm making but ...
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1answer
361 views

Pros and cons of disabling TCP timestamps

So, lynis informs me that I should unset net.ipv4.tcp_timestamps. I know that's a bad thing because an attacker could figure out which updates that require restarting the machine I haven't applied, or ...
8
votes
1answer
91 views

Once established, are sockets on localhost secure?

Once a TCP socket has been established on localhost, and a connection made using accept, is it possible for a non-privileged user to intercept or modify bytes sent over this connection, or can this ...
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1answer
66 views

Didn't understood what the purpose of the newly discovered TCP Faking attack

Source: http://lgms.nl/blog-2 Hey guys, I've been reading through the research paper but didn't understand the purpose of the attack. What the attacker will want to exploit here ?
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2answers
193 views

How to limit source port for accessing blocked website?

My country has a firewall which blocks sites like Facebook, whatsApp etc. However, they use some kind of port blocking, so some important websites for me like Chegg is also getting blocked I think due ...
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1answer
102 views

FIN Scan: sneak through certain non-stateful firewalls?

Many resources stated that FIN scan can bypass non-stateful firewall: In Nmap document: The key advantage to these scan types is that they can sneak through certain non-stateful firewalls and ...
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0answers
49 views

script for analysis of tcpdump log file

I'm trying to get the following metrics from my tcpdump log file: (1) one-way delay, (2) request/response delay, (3) packet loss, (4) overall transaction duration and (5) delay variation (jitter). ...
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1answer
74 views

Open TCP port on cable modem TG1672G

TG1672G cable modem in bridge mode, the modem's built in router still gets a IPv4/IPv6 public address (and devices connected to the modem can get public IPv4/IPv6 addresses too). This modem is Intel ...
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2answers
166 views

Add SSL on top of existing TCP connection

This may sound as basic question for some but I have never done such thing. Imagine I basically have simple TCP client implemented on C# (e.g. TCPClient class) and simple TCP server implemented using ...
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2answers
334 views

Spoofing TCP/IP stack OS Fingerprinting attacks in OSX

We need to change our OSX fingerprint in order to impersonate the Android OS against "passive OS fingerprinting" attacks. For Windows machines there are tools/guides for doing that, but can't find ...
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1answer
310 views

Can a Cisco ASA 5505 block this DDoS attack?

Since more than a week ago, my dedicated server (located at ovh.com) has been under TCP SYN (I think) attack. OVH don't care about it but this attack is killing my server with a high CPU load (...
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41 views

Snort signatures not working [closed]

I am using snort to detect signature for IDS but some rule not detected by snort which is highlighted below. Kindly, sort this out, I'm stuck here.
2
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1answer
65 views

Types of risks for my router

Recently I've read about viruses and worms that attack routers and do some nasty things, incl. DNS changes etc. In the beginning, I just read that some people have issues that their DNS server address ...
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1answer
35 views

NMAP's explicitely closed ports

I'm working on a challenge and I notice this odd output for a full port scan? abc@desktop:~$ nmap -T5 -p- -sV x.x.x.x -PN Interesting ports on x.x.x.x: Not shown: 65533 filtered ports PORT ...
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1answer
69 views

Find out what process is trying to initiate a connection in Windows

I'm not trying to find established TCP connections. I have a Windows 2008 R2 server and my host-based L3 firewall is showing one TCP connection ATTEMPT to a remote address. The connection is not ...
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2answers
205 views

If two programs on the same machine communicate through TCP, can it be seen from the outside?

Assume there are two programs running on the same computer at the same time. The computer is connected to a LAN. The two programs communicate via a TCP socket, and the socket is opened using the IP ...
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2answers
141 views

Should I block outbound TCP RST (on closed ports)?

I have a range of inbound TCP ports open on the firewall, but usually closed on the host machine. I see a handful of unknown connection attempts each day, for which the server returns TCP RST. I ...
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1answer
70 views

UDP Out dated and insecure [closed]

UDP has so many flaws and the "performance" benefits are small and very niche. Often times TCP is even higher performing. UDP is inherently flawed in the way in which it operates. It leaves ...
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53 views

BitTorrent: how do cracked files get blocked and why is blocking some torrents unsuccessful/inefficient?

Not sure if this is a good question for this site, but suppose someone needs to find a torrent which contains a crack (perhaps one delivered from Hong Kong where it is legal to distrubute such cracks)....
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3answers
1k views

TCP versus UDP resilience to DDoS

I am building a service that I can implement equally well with either TCP or UDP. If I use TCP, I expose vulnerability to SYN flood and other attacks on TCP protocol. If I use UDP, it will be harder ...
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2answers
55 views

Secure protocol for a backup server? [closed]

I want to make a back up system in my home, but I don't know I should use a FTP server or a TPC-based cloud server or a SSH-based server. Which method is best in security? I just want to upload and ...
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3answers
1k views

Why no support for TCP Sockets in JavaScript [closed]

I know there are now WebSockets, but what is the issue with providing a socket API to allow interacting with existing protocols? I mean, after all, I can use a hidden flash object to do the same ...
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2answers
1k views

Spoof IP adress after a TCP handshake

I know it is not possible to perform a successful TCP Handshake with a spoofed IP-Address. However I wonder: Is it possible to spoof the IP once a TCP handshake was performed successfully? For ...
4
votes
2answers
106 views

Is encryption possible for simplex (one-directional) TCP/IP, and if so, how?

As explained in the TCP/IP Guide, it is possible to configure TCP/IP to operate in simplex mode and this mode is utilized, among other things, in communication from satellites. One consideration with ...
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1answer
167 views

How to see all incoming and outgoing traffic of other nodes while on a LAN?

I've got two computers. A & B. While sitting on the computer A how can I see the incoming and outgoing traffic of computer B? Or can I? Note: Please try to answer in a non-technical language as ...
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1answer
63 views

Using a Firewall to Trigger Truncation in DNS UDP Response

Assume I am a firewall between client and server. If the client sends a DNS query with UDP, I should response this query with set the truncated flag=1. As a result, the client will be forced to use ...
3
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1answer
649 views

Is it possible to force client use TCP instead UDP for DNS queries?

Assume I am managing a firewall between DNS server and clients. Is there any way to force clients use TCP rather than UDP, so we can prevent DNS spoof types of DDoS attacks?
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1answer
107 views

Random scanning or potential attack/recon? [duplicate]

If the purpose of a SYN Flood attack would be to make the target unresponsive to normal traffic, same as any other DoS, wouldn't this attack generally have been directed at a public server rather than ...
4
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1answer
165 views

Protect password/authenticating during transit over (insecure) TCP socket for a game

Background I am designing a multi-player game with a single server that handles multiple worlds. Each player logs into the server initially before requesting which world to join. The server has a ...
3
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2answers
133 views

When should I drop a packet with ICMP type 3, code 9 or 10, TCP RST, or TCP ACK?

This answer says there are a few ways of dealing with a blocked packet at a firewall: At each of these levels a 1st IP packet (and any other protocol packet as an ESP or AH packet) might receive ...
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2answers
232 views

Malware / vulnerability that uses or causes malformed IP or TCP Headers

I'm curious if there are any examples of malformed IP or TCP headers (for example, checksums that don't match, reserved bits that aren't zero, or poor header length numbers) used by malware, or that ...