Cyber attackers use an increasingly wide range of methods and techniques to exploit vulnerabilities in various organizational systems and get their hands on precious information and data. One of the techniques they use is RCE or remote code execution. As a matter of fact, according to reliable sources such as the NTT’s Global Threat Intelligence Report of 2020, this technique was the second most prevalent attack method, followed only by injection attacks.
Needless to say, the major benefit of this attack (as the name suggests) is that attackers can infiltrate the system basically from anywhere, no matter the location. RCE can be looked at as an arm’s length offensive that allows the attackers to enter and leave the system without getting harmed but leaving the business, its system, data, and operations in massive damage. This article, as the title suggests, will aim to elaborate more on remote code execution, how it works, and what security experts should do to decrease the chances of such an attack happening.
What Is RCE (Remote Code Execution)
When comparing various cyber attacks, security experts will usually agree that remote code execution is among the most severe attacks hackers can launch on a server or an application. By definition, it means the ability to gain access to and modify a given system without having been given any authority and regardless of location. In short, remote code execution enables hackers to take over the entire system or server with the help of arbitrary malicious software.
Hackers will often exploit this vulnerability by writing malicious code, which they inject into servers with the help of an input. The server will usually unknowingly execute the command, allowing hackers to access the system. Following this, the attackers might even try to gain even more privileges within the system, which might even lead to the complete compromise of the application or server.
How Does RCE Work?
By now, you can see that an RCE attack should not be taken lightly. But, how can hackers infiltrate the system with such ease and eventually take it over? In order to gain access, the intruder must exploit a remote code execution vulnerability to inject the malware. This can be done by using query components, a form, uploading specific files to an app, or via cookies. Attackers are able to do this when the developers overlook the importance of implementing input data validation features and leave the applications for RCE attacks.
As such, these vulnerabilities are extremely popular among attackers who wish to execute malicious code remotely. Generally, the attack itself consists of three major steps:
- First, the attackers scan different websites, applications, and servers through the internet for known vulnerabilities that they might be able to exploit.
- When they identify a vulnerability that’s suitable for RCE, they will try to expliot it to gain access.
- After gaining access, they will execute the code on the system. This will usually enable them to alter permissions, steal info, destroy or encrypt different files, download malware, and more, all based on the system’s state, the vulnerability the attackers exploited, and the tools they used for the attack.
Code execution will usually be achieved through bash scripts and terminal commands. The attacker will inject the code into the app that will execute it itself or will rely on the kernel to perform the execution.
Remote Code Execution Attack Example
Unfortunately, remote code execution attacks are pretty commonplace, widespread, and so pervasive that it’s actually difficult to name only one good example. However, when it comes to the most massive damage these attacks caused, there are a few memorable examples that can demonstrate just how devastating these attacks can be.
One such example occurred on the 9th of December. More specifically, the Apache Foundation released an emergency update for a serious zero-day vulnerability in the widely popular logging tools named Log4j that comes mostly default in several Java-powered apps. The vulnerability issue was named Log4Shell and got the CVE-2021-44228 identifier.
The exploitable vulnerability itself is related to a bug in the tool’s library. More precisely, the bug can allow attackers to execute arbitrary code on any system that writes out log messages via Log4j. These severe risks affected several Log4j versions, more precisely every version of Log4j 2 ( from 2.0-beta-9 to 2.15.0).
After identifying the main problem, the Apache Foundation disclosed several related risks in the tool. For instance, the CVE-2021-44832 vulnerability allows for RCE attacks if the attacker managed to modify the configuration of the tool.
RCE Attack Impacts
As mentioned before, remote code execution attacks can leave applications, servers, and systems at significant risk, potentially causing massive damages to data confidentiality and integrity. Attackers who infiltrate these systems through RCE methods with system or server privileges can:
- Change access privileges for the rest of the users
- Modify, delete, and read files and other data
- Communicate to the servers
- Modify different services and turn configurations either on or off
Preventing Remote Code Execution Vulnerabilities From Happening
Needless to say, to keep your systems, business, or organization safe in this increasingly dangerous and ever-evolving digital threat landscape, it’s pivotal to have all of the latest necessary security measures protecting your systems.
That said, the following measures and techniques can help you avoid and prevent RCE attacks.
- Unfortunately, it may not be possible to prevent every remote code execution attack, but having the necessary early alert systems in place can signal security teams to take the essential preventative measures. A good monitoring system can continuously scan the system to detect potentially malicious behaviors that can potentially compromise the server or system,
- Security tools like firewalls can potentially prevent already widespread automated hack attempts. Implementing and usingvulnerability scanning software and penetration testing tools can also fix potential entry points before an attack even takes place.
- Perform regular updates when it comes to your third-party tools, operating systems, and software. Patching your software or installing the latest versions as soon as they become available can be the best countermeasures when it comes to preventing RCE hacks.
- Interaction fields in systems should always be treated as relatively unreliable because developers don’t have any control over the data users enter.
- Limiting access to the interpreter is also a great idea. Ensure that your users only have the necessary privileges that allow them to perform their delegated tasks.
- Make sure always to use the safest practices when uploading files. Also, never let your users decide things regarding the content or the extension of the files on the webserver.
Being Up-Do-Date As The Best Defense Mechanism
By now, you probably know that remote code execution attacks can pretty much compromise an entire system, server, or application. They have the potential to cause irreparable damage and ruin the reputation of any business and organization.
In this ever-evolving threat landscape, often, the only reliable thing to do is to have the latest security measures protecting your digital assets. Working together with a dedicated security team who uses the newest software and protocols can significantly reduce the chances of suffering major losses from attacks.