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OPSEC - Security when making calls

GeneralEdward Kiledjian

RELATED: OPSEC - Introduction to Malware

RELATED: OPSEC - How to securely delete files

If you are making calls using a cellphone or landline phone then you should assume that your conversation can easily be intercepted by the carrier (providing the service or a government agency that has control over that carrier). Security researchers have even proven that with $1,500 in parts, they can build a cell phone call interception device by pretending they are a cell tower.

Regular phone calls on your cell phone (including SMS and MMS messages) are easily intercepted and should be considered insecure.

What about VOIP?

VOIP stands for Voice Over IP and any app that allows you to make voice calls is typically using VOIP (Whatsapp, Skype, DUO, etc). Many carriers have started offering Voice Over WIFI and Voice Over LTE. VOWIFI and VoLTE have the same security (or insecurity) as making a regular call using your carrier's normal cell network.

Some VOIP software offers decent or good end-to-end encryption. These require both parties to have the same software and typically callout that they use encryption in their literature. But be careful, not all encryption is created equal. Telegram Messenger advertises that it is secure but a deep dive into its model shows it uses "bad" (my opinion) encryption and shouldn't be trusted. 

RELATED: Telegram Messenger isn't as secure as you think

So some VOIP services offer good reliable encryption and others don't. Here are the ones you can rely on.

Signal

I have written about the free open-source Signal messaging app for years. Signal is the defacto reference on how to build solid end-to-end encryption. Their model was so good, they helped Whatsapp when it wanted to improve its security. 

RELATED: Whatsapp to become more secure than Apple Messages

Signal is cross-platform (Windows, Mac, ChromeOS, Chrome Browser). Signal offers a simple encrypted text messaging service and secure encrypted calling service. 

Signal uses your existing number and address book to simplify your authentication and connection with other users. Therefore there is no separate username or password to remember.

I have to highlight the fact that a motivated attacker can still collect metadata from signal calls because the central management servers are still owned by Whisper Systems. Whisper Systems does not have a way to listen in on calls or read messages but they do know who you spoke to, when and for how long. Having said this though, they still offer the most secure and best build encrypted messaging app around, and it is all offered for free.

Jitsi for encrypted video chats

If you want a free open-source tool for encrypted video chats (does audio too) then take a look at Jitsi. It also supports group chats. There is no requirement to sign-up for anything and therefore your personal information isn't sitting on some third-party server, 

You visit the site, enter a meeting name (without spaces and difficult to guess) and share that link with the other participants. It's really all there is to it. Safe, Easy and Secure.

What about Skype or Google Hangouts?

Most VOIP solutions offer transport encryption (which means a third-party like your carrier can't eavesdrop) but the data is managed unencrypted once it reaches the provider's network. In most cases, I discourage the use of these services for situations where security is the utmost priority. One caveat is that Skype has announced that it will work with the Signal team to implement end-to-end encryption (like Whatsapp did) but that is still many months away.  

There are dozens of products that use security to differentiate themselves and most have not been independently reviewed. I recommend you stick to the 2 products mentioned above.

Conclusion

Good security requires some planning but is well worth the effort. Hopefully, this article helps

OPSEC - How to securely delete files

GeneralEdward Kiledjian

You should also read my previous article "OPSEC - Introduction to Malware". 

Most computer (or smartphone/tablet) users believe that when you use the delete function in your operating system, you have securely destroyed the file beyond recovery, but that simply isn't the case. In most cases, the entry to the file was removed from the index but unless that disk space is needed by the operating system, the file is most likely still on the disk (just isn't normally accessible anymore).  The only sure way to ensure that the information is permanently deleted is by using a special process or tool that overwrites the drive. 

Let's talk about solid state drives

Note :  Deleting files from flash drives is very hard (Solid State Disks, USB keys, SD Cards, etc) The information in this post applies only to traditional spinning disks (what we call hard drives). 

The best recommendation I can make for these types of media is to use encryption as soon as you unpack the medium. 

What about Windows

The most widely recommended tool to securely delete a file or write over empty space to ensure previously deleted files aren't recoverable is a freeware tool called Eraser. Once installed, you can right-click a file or folder and choose Eraser > Erase from the right-click menu. 

You can also delete all the previously delete data from your computer by overwriting the empty space. 

What about Mac OS?

On MacOS 10.4 running on a computer with a normal hard drive, you can

  • open the Trash folder
  • Go to Finder > Secure Empty Trash

Unfortunately, in the El Capitan update, Apple removed this option because it could no longer guarantee that the new SSD disks in its devices would overwrite the files. Their comment can be found here and reads:

An issue existed in guaranteeing secure deletion of Trash files on some systems, such as those with flash storage. This issue was addressed by removing the “Secure Empty Trash” option.
— Apple blog

Apple's mitigating control is that they encrypt the entire disk using FileVault and thus without your password, the data would look like jibberish anyway. 

What do I do before selling my computer?

Regardless if you use a Windows or Mac machine, or if you use a hard disk or more modern SSD, the key is to remove the storage medium from the machine before you sell it. Then physically destroy the disk. In the commercial space, we use specialized disk shedders but you can drill holes in it then bank the daylights out of it with a hammer. Just remember to be safe.

How do I dispose of CD-ROMs or DVDs?

Most office supply stores sell inexpensive paper shedders that also shred (or in most cases physically destroy the storage medium) of CD-ROMs and DVDs. I recommend you invest in one of those or physically break the disk into hundreds of pieces using pliers.

OPSEC - Introduction to Malware

GeneralEdward Kiledjian

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.

  • 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, Download.com, 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).