Script Attacks.. Encyclopaedia

Attackers always seek out new ways to evade detection. As most endpoint security products handle file-based attacks relatively well, scripts are an excellent way for attackers to avoid making changes to a disk, thus bypassing the threat detection capabilities of most products. In today’s threat landscape, scripts provide initial access, enable evasion, and facilitate lateral movements post-infection.

Script-based attacks

A script can be anything from a sequence of simple system commands, advanced scripting languages used for system configurations, complex task automation, and other general purposes. Common scripting languages are VBScript, JavaScript, and PowerShell. Unlike applications that run after being compiled into machine code, computers interpret scripts.

How attackers use scripts

Payload delivery and lateral movement follow a successful script-initiated infection. The payload performs actions desired by the attacker, such as information collection, file encryption, or backdoor communication. At the same time, lateral movement leads to infection of additional computers within the network.

The use of scripts poses many advantages to the attacker: scripts are easy to write and execute, trivial to obfuscate, and extremely polymorphic. Moreover, attackers can use many types of script files to carry out an attack – the most popular being PowerShell, JavaScript, HTA, VBA, VBS, and batch scripts. Since fileless attacks occur in memory, traditional static file detection is rendered useless.

Script-based attacks run on virtually all Windows systems, increasing the potential attack surface and the chance of infection. One major drawback of script-based attacks is that, unless deployed via an exploit, user interaction is required for the script to run.

Many types of malware use scripts. For instance, a script that downloads a PE file can either save it to disk or run it from memory, depending on its level of sophistication. The script can also perform additional malicious actions, such as collecting information about the victim, from the computer name to saved passwords.

PowerShell

PowerShell is a framework used for configuration management and task automation, with a command-line shell and scripting language. PowerShell provides access to Microsoft Windows Management Instrumentation (WMI) and Component Object Model (COM), which makes it a useful and versatile tool for system administrators automating IT management processes, but also for attackers seeking a foothold in the system.

A malicious file loader using PowerShell

Attackers use poweshell in their attacks to load malware directly in memory without writing to disk, thus bypassing many endpoint security products. Attackers also use PowerShell to automate data exfiltration and infection processes using frameworks such as Metasploit or PowerSploit.

As with other types of attacks, in a script-based attack, the initial hold of the victim generally occurs through a successful phishing attack, which contains a dropper – such as a PDF, RTF, Office file, or archive. In most cases, the dropper will then run a script, either a VBA macro or another type of script, such as PowerShell, JavaScript, or HTA.

JavaScript

JavaScript is a standard scripting language used in web pages, web applications, and browsers. JavaScript can manipulate and modify PDF files with implemented objects, web page links, and more. Most PDF-based attacks use the PDF reader software or an in-browser reader to run JavaScript code on the victims’ machine.

Additional script-based threats

HTML application (HTA) is a Microsoft Windows file meant to run on Internet Explorer, which combines HTML code with Internet Explorer-supported scripts such as VBScript or JScript. HTA files execute through Microsoft HTA engine (mshta.exe) that has the local user’s privileges instead of Internet Explorer’s restricted privileges, with access to the filesystem and registry.

Malicious HTA files allow scripts to run the machine with local user privileges to download and run executables or additional scripts. Though considered an old attack vector, many script-based attacks continue to use HTA files. These files can be sent as attachments, downloaded by another script, or redirects from malicious websites.

Scripts to run in network is that safe ?

With script-based attacks on the rise, organizations need to be ready to combat attacks in which the entire attack sequence occurs in memory.

A basic first step any organization should consider is segmenting employees into several groups:

1. Running scripts is part of their day-to-day job
2. Running scripts is not common but might happen
3. There is no need to run scripts

With these foundational rules in place, organizations should seek out security solutions with specific capabilities that balance the ability to detect script-based attacks while allowing users who need to use scripts for their job function to do so without interruption.