Understanding reverse shells
Shell Game
Firewalls block shell access from outside the network. But what if the shell is launched from the inside?
Recently, I've thoroughly enjoyed brushing up my offensive security skills. I've worked in the defensive security field for longer than I care to remember, and gaining more insight into how attackers perceive the world has really opened my eyes. My background is two-and-half decades of Linux and securing containers over the last seven years or so. An area that always piques my interest is Linux-based local privilege escalation. Once you have found a way of gaining access to a machine, the Holy Grail is elevating your privileges to the root user so you have full control.
Sometimes achieving root can take a little time. As an attacker, it is important to be able to return at a later date if you haven't achieved root user privileges yet or you want to monitor changeable data on a machine. Penetration testers and attackers would call this ongoing access persistence, which is the ability to gain a foothold and then maintain access; you might also call it creating a backdoor.
Attackers have a multitude of ways for ensuring that, if a machine reboots or some other event occurs, a backdoor is re-established automatically. This article looks at reverse shells and provides some examples of how to achieve persistence once you have gained access to a Linux machine. It should go without saying that you should use the following information for testing, practicing, and improving your knowledge and not for some nefarious purpose.
[...]
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
-
Canonical Releases Ubuntu 24.04
After a brief pause because of the XZ vulnerability, Ubuntu 24.04 is now available for install.
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.