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Evasion Server.rar



Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics and techniques are cross-listed here when those techniques include the added benefit of subverting defenses.




Evasion Server.rar



Brushaloader is an evolving threat that is being actively developed and refined over time as attackers identify areas of improvement and add additional functionality. We have identified multiple iterations of this threat since mid-2018. Most of the malware distribution activity that we observe associated with Brushaloader leverages malicious email campaigns targeting specific geographic regions to distribute various malware payloads, primarily Danabot. Danabot has already been described in detail here and here, so this post will focus on the analysis of Brushaloader itself. Talos has recently identified a marked increase in the quantity of malware distribution activity associated with Brushaloader, as well as the implementation of various techniques and evasive functionality that has resulted in significantly lower detection rates, as well as sandbox evasion.


As far as the attachment itself, it typically consists of a RAR file with a filename that contains the word "faktura." The RAR files typically contain a VBScript that reaches out for additional payloads. The script itself already had some interesting techniques associated with sandbox or network simulation evasion, which we will discuss later in the blog. This script wasn't heavily obfuscated, and efficiently established command and control (C2) communication with a hard-coded IP address via HTTP using wscript. The specific URL being queried in this particular campaign was:


Here, the actors have added google[.]com to the potential sources of C2 communication. Over the next several months, the legitimate site changed to include such sites as www[.]ti[.]com and www[.]bbc[.]com, among others. This was yet another simplistic approach at sandbox evasion where, periodically, the VBScript would do nothing more than send a request to a legitimate domain.


This check and functionality were relatively short-lived, since in the last couple days of October, the actors shifted away from WScript entirely and shifted the majority of the functionality to Internet Explorer directly. In addition to switching to Internet Explorer for web communications, the VBScript was streamlined considerably and went from being a 4KB text file to being less than 1KB. Below is a screen capture of the entire VBScript. A majority of the checking and evasion techniques were removed, except some extended sleep commands to timeout some sandbox technologies.


This campaign ended the first week of February and the activity has been mostly dark since then. Over the last half year, Brushaloader has gone from a new VBScript-based loader with some basic evasion techniques to an increasingly advanced and increasingly distributed threat. The timeline below illustrates how aggressive the development of Brushaloader has been. If the past is any indication, Brushaloader will be an interesting threat to follow going forward.


This is also a key example of the levels of obfuscation and sophistication these loaders can posses. This simple VBS based campaign implemented several clever evasion and obfuscation techniques in a minimal amount of code, showing that adversaries will continue to think outside the box and develop novel ways to deliver threats to users. This is why users need organizations with visibility around the world, since it's just a matter of time until this successful loader starts being sought out by other attackers looking to deliver threats. We will continue to monitor this threat and the payloads it provides and will continue to be vigilant in protecting our customers from any evolutions that will inevitably occur.


At this point, TrickBot has gained initial access and execution on the system.Then it has performed privilege escalation via a UAC bypass and defensive evasion by disabling security controls and tools. Now, the malware effectively owns the system and can launch one of its many modules to steal data, harvest credentials, inject malicious code into banking websites, launch a ransomware payload, etc.


Alternative Data Streams (ADS) are a property of every entry on the Master File Table (MFT) of NTFS formatted file systems, that can be used to store arbitrary data. When used maliciously, this can be abused as a defense evasion and code execution technique, by hiding complete files from normal methods of detection, and providing the ability to access them at a later time.


Timestomping is a technique where the timestamps of a file are modified for defence evasion. Threat actors often perform this technique to blend malicious files with legitimate files so that when an analyst is performing IR, critical evidence escapes detection.


Andromeda, also known as Gamaru and Wauchos, is a modular and HTTP-based botnet that was discovered in late 2011. From that point on, it managed to survive and continue hardening by evolving in different ways. In particular, the complexity of its loader and AV evasion methods increased repeatedly, and C&C communication changed between the different versions as well.


We used a combination of custom crafted malware and well-known malware such as Poison Ivy, metasploit, and more. We used simple A/V evasion to get around it and we NEVER turned it off. RESULT-> NOT A PEEP from A/V. Yes it was installed correctly as it did detect the un-armored metasploit payload quickly and killed it (a test to make sure it DID in fact work as I became worried it really didn't work or was setup wrong). I would gladly let anyone from McAfee look at our setup to make sure we didn't make a mistake, but I followed their guide to the letter and used recommended settings when installing the product (They took us up on that, and we sent in the logs from all 4 systems). I also have found a lot of clients with incorrect installed Enterprise products, so it is clearly possible I mundged something up during the install. If we are wrong, then we are wrong and we can go back and do run through it again after we apply their suggestions as we have it snapshotted inside an ESX server. I was actually anticipating it would find at least ONE thing we did. Nothing was found.


We used a combination of custom crafted malware and well-known malware such as Poison Ivy, metasploit, and more. We used simple A/V evasion to get around it and we NEVER turned it off. RESULT-> NOT A PEEP from A/V. Yes it was installed correctly as it did detect the un-armored metasploit payload quickly and killed it (a test to make sure it DID in fact work as I became worried it really didn\'t work or was setup wrong). I would gladly let anyone from McAfee look at our setup to make sure we didn\'t make a mistake, but I followed their guide to the letter and used recommended settings when installing the product (They took us up on that, and we sent in the logs from all 4 systems). I also have found a lot of clients with incorrect installed Enterprise products, so it is clearly possible I mundged something up during the install. If we are wrong, then we are wrong and we can go back and do run through it again after we apply their suggestions as we have it snapshotted inside an ESX server. I was actually anticipating it would find at least ONE thing we did. Nothing was found.


Cyber-attacks are becoming more sophisticated and thereby presenting increasing challenges in accurately detecting intrusions. Failure to prevent the intrusions could degrade the credibility of security services, e.g. data confidentiality, integrity, and availability. Numerous intrusion detection methods have been proposed in the literature to tackle computer security threats, which can be broadly classified into Signature-based Intrusion Detection Systems (SIDS) and Anomaly-based Intrusion Detection Systems (AIDS). This survey paper presents a taxonomy of contemporary IDS, a comprehensive review of notable recent works, and an overview of the datasets commonly used for evaluation purposes. It also presents evasion techniques used by attackers to avoid detection and discusses future research challenges to counter such techniques so as to make computer systems more secure.


The evolution of malicious software (malware) poses a critical challenge to the design of intrusion detection systems (IDS). Malicious attacks have become more sophisticated and the foremost challenge is to identify unknown and obfuscated malware, as the malware authors use different evasion techniques for information concealing to prevent detection by an IDS. In addition, there has been an increase in security threats such as zero-day attacks designed to target internet users. Therefore, computer security has become essential as the use of information technology has become part of our daily lives. As a result, various countries such as Australia and the US have been significantly impacted by the zero-day attacks. According to the 2017 Symantec Internet Security Threat Report, more than three billion zero-day attacks were reported in 2016, and the volume and intensity of the zero-day attacks were substantially greater than previously (Symantec, 2017). As highlighted in the Data Breach Statistics in 2017, approximately nine billion data records were lost or stolen by hackers since 2013 (Breach_LeveL_Index, 2017). A Symantec report found that the number of security breach incidents is on the rise. In the past, cybercriminals primarily focused on bank customers, robbing bank accounts or stealing credit cards (Symantec, 2017). However, the new generation of malware has become more ambitious and is targeting the banks themselves, sometimes trying to take millions of dollars in one attack (Symantec, 2017). For that reason, the detection of zero-day attacks has become the highest priority. 041b061a72


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