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OPSEC - Introduction to Malware

GeneralEdward KiledjianComment

What is malware

Malware is shorthand for Malicious Software and has been around almost from the start of computing. Its main purpose is to harm the computer or the user. Malware has been known to steal login credentials, monitor the user, tamper with information (breaking integrity), steal information or just making the system unusable. 

Malware can be designed by a nefarious teenager in his mother's basement looking to make a name for himself or by a state-sponsored threat actor against activists or journalists.

How can I tell if my computer is infected

The first rule of thumb is to use the Antivirus product that came with your operating system. As an example, all modern Windows systems are shipped with a self-updating antivirus supported by Microsoft. Third party products have been known to cause issues (here, here, etc).

To be transparent, antivirus will detect standard run of the mill type of malware but anything more sophisticated will easily get through. Larger companies with well-funded security teams typically eschew antivirus for more advanced malware detection tools based on a series of technologies like application behaviour monitoring, machine learning, artificial intelligence and system baselining. Unfortunately, these are not yet available for small operations but expect them to eventually make their way there.

So the question of detecting malware on your computer is a difficult one and often requires a highly skilled technician with precise tools that knows what he/she is looking for.  At the very least, use the tools available to you now:

warning I received when someone in Sao Paulo tried to log into my Lastpass account.

warning I received when someone in Sao Paulo tried to log into my Lastpass account.

  • Sign up for services that offer 2-factor authentication (so malware can't log into your account by simply stealing a password) and that will notify you of unusual behaviour (Google, LastPass, etc). 
  • Notice subtle indicators. Pay attention to your computer and look for subtle inconsistencies. Does your webcam light turn on when you are not using it? Does it look like you sent an email you don't remember sending? Does an online service show a login time you know you weren't working?  Pay attention to subtle cues.

How did I get infected?

The most common technique used by threat actors is to trick the user into installing malware pretending to be something else. It can pretend to be a system update. It can pretend to be a holiday card from a family member. It can pretend to be a work file from your boss. It can be a drive-by download where your system is exploited simply by being vulnerable and you visiting a carefully crafted webpage. 

  • Link to a malware site can be disguised as a link to a popular internet site (Apple, Amazon, Microsoft), shared content (a document, holiday card, music file, etc) or a fake system update (flash update, etc).
  • You may be targetted via email. It is common for highly skilled threat actors to compromise the systems of people you trust and use that trust to trick you into running malware, visiting a malware site or performing an action you otherwise would not. Remeber that these are often highly skilled practitioners that understand human psychology and will exploit it as needed. This includes chat apps, email, messages on forums, web pages, etc.
  • You can get infected by connecting purpose-built attack hardware to your computer. We have devices that look normal (like the USB Rubber Ducky from Hak5) but that can run attack code without your knowledge as soon as they are connected to your computer. 
  • Someone can gain physical access to your computer and plant malware without your knowledge. In security we consider it game over if anyone has access to your equipment, This is why companies spend large sums of money physically protecting their servers in isolated access controlled cages inside heavily guarded and secured datacenters. 

The more valuable you are as a target the less likely you are to notice the attack. 

How can I protect myself from malware?

  • Make sure you are running legally registered versions of all the products you use daily. Using legal versions entitles you to the latest updates and every security person will recommend keeping all of your software and operating systems updates regularly. Threat actors will often exploit vulnerabilities that have been patched (aka if you update you are protected). 
  • Only install the software you absolutely need. Remember that every software is a potential attack vector. Install only what you need and only download it from the manufacturer never from a download site like CNET,, etc (to prevent supply chain attacks like CCleaner.) Many of these download sites make money by bundling garbage apps that get silently installed and these can also be used to attack you.
  • Remember that anything you open or click on can compromise your security. Call a sender before opening a file. Download and scan it first with something like VirusTotal before opening it. Never click on links in email or instant messaging. Always go to the URL yourself (obfuscating a malicious link to look 'good' is easy). If you use Gmail, open questionable attachments in Google docs or sheets as this will often strip the malicious content.
  • Remember that one second of forgetfulness is all it takes. Be extra vigilant when browsing the web. Never run anything on the web. Always know that the web can be faked. Even known sites can be compromised and used to inject malware.
  • When travelling to high-risk areas, I usually travel with a Google Chromebook. It auto updates itself. There are very few known attacks against it. Chromebooks have a feature called Powerwash that factory resets the device image to "like new" within 2 minutes. Often times I will powerwash my device before performing sensitive tasks. Also, data is stored in the Google cloud. Regardless of how you feel about their privacy policies, they have proven to be excellent at protecting their users from targeted attacks. Make sure you turn on 2-factor authentication.
  • Turn off your computer and unplug it from a physical network when not in use.

What can I do if I am infected?

  • The first rule is that if you are infected or even suspect that you are infected, forget about cleaning your device and have it completely reinstalled from scratch using known clean installation media. 
  • If you are infected, immediately unplug your computer from the internet (ethernet or WIFI) and shut down your computer.
  • Use a known clean computer to log into your web services and change all your passwords immediately.  
  • If one of your devices is compromised, and you are a high target, assume all your other devices could be compromised and reinstall everything from scratch including your smartphone.
  • If you have support from a government agency, reach out to them and ask them for support. If you are a journalist or activist, reach out to one of the public security support organizations like the Toronto Citizen Lab
  • If you know when you were infected, make sure you restore files from a date prior to the infection. It is critically important to use a backup service that provides version control (e.g. blackblaze version control).