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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Can't identify the attack ? [on hold]

I've checked the attack type from this packet (721619.pcap) and now I'm impossible to identify this attack. Cloudshark link ( https://www.cloudshark.org/captures/50e23e13bb31 ). ip.src == ...
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0answers
33 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
119 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 ...
3
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0answers
49 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 ...
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0answers
18 views

FIN Flag - Evade Firewall [duplicate]

I would want to understand how which setting a FIN Flag. That flag closes the connection. Can someone explain me how FIN Scan do it?
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1answer
66 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
65 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
95 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
56 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
32 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
59 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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1answer
79 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
168 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 ...
4
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1answer
161 views

Block this DDoS attack

since more than a week 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 (permanent ...
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0answers
29 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
votes
1answer
56 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 ...
1
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1answer
29 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 ...
2
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1answer
50 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 ...
7
votes
2answers
126 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 ...
4
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2answers
80 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
50 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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0answers
45 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 ...
3
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3answers
618 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
48 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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votes
3answers
314 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
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2answers
101 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
138 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
45 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
322 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
96 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
votes
1answer
111 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 ...
4
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2answers
109 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
154 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 ...
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1answer
18 views

What TCP-level commands affect the global configuration of the stack?

I'm looking at TCP, and what options may affect the global configuration so that I can detect a repeat visitor. What TCP commands (for lack of a better word) affect the global TCP stack? Or that or ...
2
votes
1answer
105 views

Security over multi-streaming such as SCTP

I refer to multi-streaming as the ability to send two or more streams of some unit of data (block, byte streams) in one established association/context. SCTP is an example and the protocol I was ...
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1answer
82 views

how can the hacker benefit from the information of checking tcp port or udp port? [closed]

I studying a scanning and I want to ask how can the hacker benefit from the information of checking tcp port or udp port?
2
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1answer
100 views

Abnormal SYN traffic from Blackhole DNS servers

I have been getting alerts from an anomaly based signatures for abnormally high SYN traffic. The traffic is coming from blackhole DNS servers. I hadn't had any experience with Blackhole servers prior ...
2
votes
1answer
142 views

Does SSL or HIP solve all TCP/IP security problem?

I recently read this paper "A Look Back at Security Problems in the TCP/IP Protocol Suite" (https://www.cs.columbia.edu/~smb/papers/acsac-ipext.pdf) explaining few attacks at the TCP/IP stack. One ...
2
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2answers
52 views

Any way to circumvent a 'filtered' response on NMap?

I know that a filtered response on NMap means that the firewall dropped the packets or that NMap just didn't receive a response, but is there any way to circumvent this? Is it possible that the ...
0
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1answer
136 views

Which systems in a network are able to spoof a TCP handshake?

I am reviewing for my final exam tomorrow, I came across a past exam question. An attacker wants to initiate a TCP handshake with a target to make him think E initiated it, attacker knows IP ...
1
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1answer
45 views

Things to do to ensure that data is secured on my virtual server [closed]

I'm not much of a server administrator but I'm maintaining a virtual server with Ubuntu OS where my website is hosted. I often use ssh, ftp and MySQL. As my website gets popular, I want to make sure ...
7
votes
2answers
135 views

Why do ISPs allow faked source IP addresses?

Ok so apparently you can specify a source IP when doing a SYN request or something. Besides just asking why in the world that would even be allowed, I will move past that because I want to understand ...
5
votes
3answers
364 views

Can you sniff traffic to ip address from outside of your network?

I am not sure what it is called or even if it is possible but here is the scenario I am curious about: I login to a site that does not use SSL/TLS to do some work (unfortunately I must use this site ...
2
votes
0answers
139 views

Random SYN_SENT connections to Amazon EC2?

I have looked around but couldn't find anyone else with this issue. On my console (standard asus i7 laptop) running Ubuntu 14.04 LTS - I noticed in tcptrack that there are a lot of connections being ...
4
votes
3answers
778 views

Secure communication between two applications on the same system

I'm writing a software which is divided into two separate stand-alone pieces. One is a service like application that handles all the logics, the other one is a GUI application that just works as a ...
1
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1answer
71 views

UDP-Only Linux Dedicated Server?

I am running my own small UDP linux service on a dedicated server. my service responds to single-package requests with single-package responses. I don't want this server to do anything else. I ...
4
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1answer
201 views

Why does my web server receive so many TCP resets from some clients?

I run a web server and log connections that are dropped. Occasionally, I get a burst of TCP RST packets from some of my clients, like this: Feb 11 11:56:29 SRC=1.2.3.4 TTL=57 SPT=38383 DPT=80 ...
3
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3answers
4k views

FIN Attack- What is this type of attack really?

I just wanted to know what exactly is the FIN attack. I know about the FIN flag that is used to indicated the closing of a connection via TCP. But what exactly is FIN attack?
5
votes
1answer
250 views

Explain the last part of how Mitnick hacked Tsutomu Shimomura with an IP sequence attack

I was reading up on why TCP ISNs need to be randomized, which led me to this write up by Tsutomu Shimomura. I understood how IP address spoofing and predicting the ISN helped the attacker establish a ...