Understanding and preventing TCP attacks
HIJACK PREVENTION
It is quite easy to take a TCP connection down using a RST attack, and this risk increases with applications that need long-term connections, such as VPNs, DNS zone transfers, and BGP. We’ll describe how a TCP attack can happen, and we’ll show you some simple techniques for protecting your network.
Since 1985, experts have known that the Transmission Control Protocol (TCP) is unsafe. Attackers can take down, corrupt, or even hijack existing TCP connections armed with just a few basic details of the connection: the source IP address, the target address, and a valid sequence number. If an attacker is able to sniff the connection, the battle is over before it begins. If the attacker can’t do so, because they don’t control a machine in the path between the client and the server, things become a little more complicated. However, people have definitely overestimated the effort required to undermine a connection, and tricks like TCP windowing make remote manipulation even easier. One of the most difficult issues, is that of guessing the right sequence numbers. This is the only way to convince the target machine that the injected IP datagrams really belong to the current TCP connection. If an attacker has the right values, there is nothing to stop him from injecting data into the existing connection, thus gaining unauthorized access to information or taking down the connection by transmitting a packet with the Reset flag (RST) set.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Red Hat Releases RHEL 10 Early
Red Hat quietly rolled out the official release of RHEL 10.0 a bit early.
-
openSUSE Joins End of 10
openSUSE has decided to not only join the End of 10 movement but it also will no longer support the Deepin Desktop Environment.
-
New Version of Flatpak Released
Flatpak 1.16.1 is now available as the latest, stable version with various improvements.
-
IBM Announces Powerhouse Linux Server
IBM has unleashed a seriously powerful Linux server with the LinuxONE Emperor 5.
-
Plasma Ends LTS Releases
The KDE Plasma development team is doing away with the LTS releases for a good reason.
-
Arch Linux Available for Windows Subsystem for Linux
If you've ever wanted to use a rolling release distribution with WSL, now's your chance.
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.