A quick & dirty guide to malware (part 2: viruses)

A dialogue screen shown by Virus:W32/Duts.A

This is the second posting in a three-part series covering common threats a user may encounter.

This series serves as a rough and ready guide, highlighting key features and trends relevant to most users.

The One That Left

Last week I spoke of Trojans, Viruses and Worms as The Big Three. I lied a bit, though. Viruses – as a distinct malware type – probably shouldn’t be on that list any more.

Viruses have always loomed large in users’ minds as the poster child of malicious programs – heck, we even call it the anti-virus industry. In the last 10 years or so however, the number of virus infections has nosedived; our Labs, which once dealt with viruses routinely, now sees a proper virus infection about once or twice a month. Today when people talk of ‘viruses’, more often than not what they’re describing is technically a trojan or a worm, and they’re using the term in a general, ‘any malware will do’ kind of way.

That’s not to say viruses are extinct; we still receive a small, if persistent, number of queries about viruses. This may be because many businesses, households and users (both in developed countries and in recently connected developing ones) still use old, out-dated, unpatched machines or programs, or haven’t yet developed a security-conscious habits.

Whatever the case, virus infections will probably still cling on to life for a weary day after, so let’s take a look at them.

Highlights of a virus

Definition of a virus given by Merriam-Webster online dictionary

The Merriam-Webster online dictionary’s bare-bones definition of a computer virus touches on important elements most users should know, so I’ll just elaborate a bit more on some key concepts:

“usually hidden within another seemingly innocuous program”

Last week I compared a virus to a parasite, because not only does it ‘hide’ in another program, but also depends on its host to function. For the virus to run, the unsuspecting user must actively launch the infected program, which in turn launches the virus.

For this reason, virus writers usually create viruses that infect executable files (especially popular programs such as word processors or media files), which have a higher chance of being run; programs with files that get passed around a lot are extra attractive, since they can affect even more potential victims.

A good example is the Microsoft Office suite which, with their huge community of business and personal users, used to be a popular target for macro viruses. We still see queries related to this virus type, though thankfully far less than previously.

“Produces copies of itself and inserts them into other programs”

If you think of the common cold virus spreading from one person to another, you’ll have a pretty good idea of why this behavior can be so damaging. When a infected file is executed, it searches for and infects new files; if the newly infected files are launched, they find and infect new files in turn, like some evil Multi-Level Marketing operation. At worst, this pattern can lead to every targeted file on the system being infected.

“Usually performs a malicious action”

The damage a virus can do by replicating and infecting new files is bad enough; its payload, a completely separate set of nasty actions, can be worse. The range of actions a virus can take is huge – connecting to a remote site, changing the desktop wallpaper, displaying silly notification messages, deleting data files…it really just depends on the virus author’s imagination and programming skills.

If you’re lucky, they’re not that good and you get failed viruses like Virus:W32/Stardust; if they’re good, then you get really nasty beasts like Virus:W32/Virut or Virus:W32/Sality.AA (one of the few viruses we still find regularly active).

Appending, prepending, cavity…who cares?

A dialogue screen shown by Virus:W32/ZMK

With thousands of unique viruses out in the wild, antivirus companies find it necessary to divide them into sub-types. Unlike trojans though, viruses don’t fall into neat categories reflecting their actions; instead, they naturally fall into groupings based on technical differences in the way they infect a file – which is  basically gobbledeegook to a user not interested in detailed analysis.

Gnerally, viruses can be divided into two groups – system infectors and file infectors. The majority of viruses are the latter and infect programs or data files. System infectors on the other hand write their malicious code to specific, critical sections of the hard disk containing the operating system, so that while the OS is running its normal routines, it’s also unintentionally executing the virus code.

Fortunately, for most users a virus’s classification is largely academic. For better or for worse, the sheer variety of possible effects each unique virus can have on a file or system makes it more practical to take each virus on a case by case basis.

Back to what’s important – why should the user  care?

So let’s go back to the original question that sparked off this series: do you really need to know if it’s a virus – as opposed to, say, a trojan or worm – infecting your computer?

Well, it helps to know because the two malware types tend affect your data and computer in different ways. As a (very) general rule, trojan infections is more about data theft and loss of control over the computer; virus infections tend to result in software disruptions or damage.

Trojans may copy and steal your data, but they don’t usually destroy the data file itself; they may stop programs from running but they don’t destroy the program. A virus on the other hand, insert its own code into a program or data file, and depending on how it does so, may either leave the host completely unharmed and functional, slightly disrupted, or completely non-functional.

Another difference between trojans and viruses that really affects the user involves disinfection. For one thing, a trojan is usually a single, discrete program – getting rid of it tends to be fairly simple, a matter of removing the malicious file and its residuals (registry keys, processes, icons, etc). Removing the trojan also generally doesn’t affect the integrity of other files on the computer.

Viruses are far more nebulous by design – they can be present in multiple files, in different locations. Identifying a virus-infected file may require scanning the entire computer to be sure every affected file is caught. Removing malicious code from an infected file or – if it can’t be saved, deleting the infected file entirely – can also be problematic if the damaged data is important or the program is a critical system component.

And this doesn’t even take into account the virus’s payload, which can produce a whole other set of worries.

If you’re still interested

Still, there is a ray of hope. If current malware trends persist, we may soon see adware or backdoors promoted to being the newest member of The Big Three, and viruses – as a distinct malware type – can finally be relegated to joining 3½” floppy disks in Computer Hell.

In the meantime, here’s some links to other, more in-depth resources on viruses:

Or partially available on Google Books:

  • “Elements of Computer Security” by David Salomon
  • “Cybercrimes: A Multidisciplinary Analysis” by Sumit Ghosh


Coming soon – Worms!

More posts from this topic


5 things you need to know about securing our future

"Securing the future" is a huge topic, but our Chief Research Officer Mikko Hypponen narrowed it down to the two most important issues is his recent keynote address at the CeBIT conference. Watch the whole thing for a Matrix-like immersion into the two greatest needs for a brighter future -- security and privacy. [youtube https://www.youtube.com/watch?v=VFoOvpaZvdM] To get started here are some quick takeaways from Mikko's insights into data privacy and data security in a threat landscape where everyone is being watched, everything is getting connected and anything that can make criminals money will be attacked. 1. Criminals are using the affiliate model. About a month ago, one of the guys running CTB Locker -- ransomware that infects your PC to hold your files until you pay to release them in bitcoin -- did a reddit AMA to explain how he makes around $300,000 with the scam. After a bit of questioning, the poster revealed that he isn't CTB's author but an affiliate who simply pays for access to a trojan and an exploit-kid created by a Russian gang. "Why are they operating with an affiliate model?" Mikko asked. Because now the authors are most likely not breaking the law. In the over 250,000 samples F-Secure Labs processes a day, our analysts have seen similar Affiliate models used with the largest banking trojans and GameOver ZeuS, which he notes are also coming from Russia. No wonder online crime is the most profitable IT business. 2. "Smart" means exploitable. When you think of the word "smart" -- as in smart tv, smartphone, smart watch, smart car -- Mikko suggests you think of the word exploitable, as it is a target for online criminals. Why would emerging Internet of Things (IoT) be a target? Think of the motives, he says. Money, of course. You don't need to worry about your smart refrigerator being hacked until there's a way to make money off it. How might the IoT become a profit center? Imagine, he suggests, if a criminal hacked your car and wouldn't let you start it until you pay a ransom. We haven't seen this yet -- but if it can be done, it will. 3. Criminals want your computer power. Even if criminals can't get you to pay a ransom, they may still want into your PC, watch, fridge or watch for the computing power. The denial of service attack against Xbox Live and Playstation Netwokr last Christmas, for instance likely employed a botnet that included mobile devices. IoT devices have already been hijacked to mine for cypto-currencies that could be converted to Bitcoin then dollars or "even more stupidly into Rubbles." 4. If we want to solve the problems of security, we have to build security into devices. Knowing that almost everything will be able to connect to the internet requires better collaboration between security vendors and manufacturers. Mikko worries that companies that have never had to worry about security -- like a toaster manufacturer, for instance -- are now getting into IoT game. And given that the cheapest devices will sell the best, they won't invest in proper design. 5. Governments are a threat to our privacy. The success of the internet has let to governments increasingly using it as a tool of surveillance. What concerns Mikko most is the idea of "collecting it all." As Glenn Glenwald and Edward Snowden pointed out at CeBIT the day before Mikko, governments seem to be collecting everything -- communication, location data -- on everyone, even if you are not a person of interest, just in case. Who knows how that information may be used in a decade from now given that we all have something to hide? Cheers, Sandra  

Mar 23, 2015
freedome, screenshot, freedome, VPN, best privacy

The Freedome approach to privacy

We were recently asked a series of questions about how Freedome protects private data by TorrentFreak.com. Since we believe transparency and encryption are keys to online freedom, we wanted to share our answers that explain how we try to make the best privacy app possible. 1. Do you keep ANY logs which would allow you to match an IP-address and a time stamp to a user of your service? If so, exactly what information do you hold and for how long? We do not keep any such logs. If ever required by law under a jurisdiction, we would implement such a system, but only where applicable and keeping storage time to the minimum required by law of that respective jurisdiction. Note also that no registration is required to use our service, so any log information would generally map to an anonymous, random user ID (UUID) and the user’s public IP address. 2. Under what jurisdiction(s) does your company operate? Freedome is a service provided from Finland by a Finnish company, and manufactured and provided in compliance with applicable Finnish laws. 3. What tools are used to monitor and mitigate abuse of your service? We have proprietary tools for fully automated traffic pattern analysis, including some DPI for the purpose of limiting peer-to-peer traffic on some gateway sites. Should we detect something that is not in line with our acceptable use policy, we can rate limit traffic from a device, or block a device from accessing the VPN service. All of this is automated and happens locally on the VPN gateway. 4. Do you use any external email providers (e.g. Google Apps) or support tools ( e.g Live support, Zendesk) that hold information provided by users? We do not use any external email providers, but our users can, for example, sign up for beta programs with their email address and send us feedback by email. The email addresses are used only to communicate things like product availability. In the future, paying customers can also use our support services and tools such as chat. In those cases, we do hold information that customers provide us voluntarily. This information is incident based (connected to the support request) and is not connected to any other data (e.g. customer information, marketing, licensing, purchase or any Freedome data). This data is purely used for managing and solving support cases. 5. In the event you receive a DMCA takedown notice or European equivalent, how are these handled? There is no content in the service to be taken down. Freedome is a data pipeline and does not obtain direct financial benefit from user content accessed while using the service. While some of the other liability exclusions of DMCA (/ its European equivalent) apply, the takedown process itself is not really applicable to (this) VPN service. 6. What steps are taken when a valid court order requires your company to identify an active user of your service? Has this ever happened? The law enforcement data requests can effectively be done directly only to F-Secure Corporation in Finland. If a non-Finnish authority wants to request such data from F-Secure, the request will be done by foreign authorities directly to Finnish police or via Interpol in accordance to procedures set out in international conventions. To date, this has never happened for the Freedome Service. 7. Does your company have a warrant canary or a similar solution to alert customers to gag orders? We do not have a warrant canary system in place. Instead, Freedome is built to store as little data as possible. Since a warrant canary would be typically triggered by a law enforcement request on individual user, they are more reflective on the size of the customer base and how interesting the data in the service is from a law enforcement perspective. They are a good, inventive barometer but do not really measure the risk re: specific user’s data. 8. Is BitTorrent and other file-sharing traffic allowed on all servers? If not, why? BitTorrent and other peer-to-peer file sharing is rate limited / blocked on some gateway servers due to acceptable use policies of our network providers. Some providers are not pleased with a high volume of DMCA takedown requests. We use multiple providers (see Question #12) and these blocks are not in place on all the servers. 9. Which payment systems do you use and how are these linked to individual user accounts? There are multiple options. The most anonymous way to purchase is by buying a voucher code in a retail store. If you pay in cash, the store will not know who you are. You then enter the anonymous voucher code in the Freedome application, and we will then confirm from our database that it is a valid voucher which we have given for sale to one of our retail channels. The retail store does not pass any information to us besides the aggregate number of sold vouchers, so even if you paid by a credit card, we do not get any information about the individual payment. For in-app (e.g., Apple App Store, Google play) purchases you in most cases do need to provide your details but we actually never receive those, we get just an anonymous receipt. The major app stores do not give any contact information about end users to any application vendors. When a purchase is made through our own e-store, the payment and order processing is handled by our online reseller, cleverbridge AG, in Germany. Our partner collects payment information together with name, email, address, etc. and does store these, but in a separate system from Freedome. In this case we have a record who have bought Freedome licenses but pointing a person to any usage of Freedome is intentionally difficult and against our policies. We also don’t have any actual usage log and therefore could not point to one anyway. 10. What is the most secure VPN connection and encryption algorithm you would recommend to your users? Do you provide tools such as “kill switches” if a connection drops and DNS leak protection? Our application does not provide user selectable encryption algorithms. Servers and clients are authenticated using X.509 certificates with 2048-bit RSA keys and SHA-256 signatures. iOS clients use IPSEC with AES-128 encryption. Other clients (Android, Windows, OS X) use OpenVPN with AES-128 encryption. Perfect Forward Secrecy is enabled (Diffie-Hellman key exchange). We provide DNS leak protection by default, and we also provide IPv6 over the VPN so that IPv6 traffic will not bypass the VPN. Kill switches are not available. The iOS IPSEC client does not allow traffic to flow unless the VPN is connected, or if the VPN is explicitly turned off by the user. The Android app, in “Protection ON” state keeps capturing internet traffic even if network or VPN connection drops, thus there is no traffic or DNS leaks during connection drops. If the Freedome application process gets restarted by the Android system, there is a moment where traffic could theoretically leak outside the VPN. Device startup Android 4.x requires user’s consent before it allows a VPN app to start capturing traffic; until that traffic may theoretically leak. (Android 5 changes this, as it does not forget user’s consent at device reboot.) 11. Do you use your own DNS servers? (if not, which servers do you use?) We do have our own DNS servers. 12. Do you have physical control over your VPN servers and network or are they outsourced and hosted by a third party (if so, which ones)? Where are your servers located? In most locations we utilize shared hardware operated by specialized hosting vendors, but we also have our own dedicated hardware at some locations. Providers vary from country to country and over time. In some countries we also use multiple providers at the same time for improved redundancy. An example provider would be Softlayer, an IBM company whom we use in multiple locations.

Mar 18, 2015

ICE in your mobile. Sounds great, but is it really a good idea?

Another Internet and Facebook chain letter you no doubt have seen. Paramedics recommend adding a contact record named ICE in your mobile phone. It stands for In Case of Emergency and helps contacting your closest relatives if you have an accident. Sounds great, but let’s take a closer look first. This is actually not a typical hoax chain letter because it’s based on facts. The idea emerged in UK in 2005, and was indeed introduced by paramedics. It’s a novel idea with good intentions and might have worked in the era before the smartphone. But it’s badly outdated now. I sincerely hope that people start circulating updated instructions rather than the original 10 years old idea. Here’s why. First, ICE is a nice idea. But it’s NOT the primary interest of paramedics. Their job is to save your life. They are going to concentrate on that rather than playing with your gadget. But ICE-info may still come in handy later at the hospital when the dust settles a bit. Knowledge of some medical conditions is important to paramedics helping a trauma patient. Persons with conditions of this kind wear special medical IDs, necklaces or bracelets, and paramedics are trained to look for them. This has nothing to do with ICE. Our smartphone is a key to all our on-line accounts, e-mail, Facebook, Twitter, cloud storage, you name it. It MUST be locked with a good password, otherwise you take a huge digital risk. And that unfortunately kills the idea with an ICE phonebook record. It’s not worth leaving the phone unprotected because of the ICE-record. Don’t even consider that! Sometimes good old low-tech solutions are far better than digital technology. This is one of those cases. Write the ICE info on a sticker and put it on your phone or anything you carry with you. ID papers, like your driving license, are probably the best items as they are likely to be brought with you to the hospital. If you are a bit nerdy, like me, you may still want a digital solution. Check your mobile for a function or app that puts free form text on the lock screen and use it for ICE. Some phones may even have a separate ICE function for this purpose. But use it as a complement to the good old sticker, not as a replacement. So to summarize. ICE is in theory a good idea, but not really crucial for your survival. It’s not worth sacrificing your digital safety for it. Especially when you simply need a pen and paper to create an ICE record that is more reliable, safer and easier to use!   Safe surfing, Micke   PS. Full medical ID can also be put on the mobile’s lock screen, at least on Android and iPhone. I’m not sure if this is a good idea. A solid necklace of stainless steel somehow feels better for stuff that can mean the difference between life and death. A complement to the necklace is of course never wrong but I really hope that nobody who really needs it trust this as their only medical ID!   Image by Ragesoss through Wikimedia  

Mar 16, 2015