How Windows pc and Mac systems get infected

Why Windows malware is not posing a threat to Linux system

In this post I will make an attempt to create a synopsis of usual ways malware makes its way into Windows or Mac system. I am referring specifically to Win/Mac because the vast majority of viruses and other malware is created for these two aforementioned Operating Systems, MS Windows being particular favourite of malware writers due to its large share of OS market (that is, if we are not talking mobile phones at this point).
Malware that has been created for Windows pc, is designed for Registry based OS, and neither Linux or Unix is one, therefore, cannot become affected by it (that is one of the few reasons why I absolutely love Linux). Even though malware can affect only OS it has been designed for, there are couple of things often shared by all three most popular computer Operating Systems (as well as those found in majority of mobile smartphones): Adobe Flash and Sun Java. (In case of Linux the use of Adobe product is less common though.) Even though HTML5+DOM coding in website development is expected to eventually make the use of Flash obsolete, currently that is not the case.

Top weaknesses that can cause infection

1. Unpatched security holes.

Operating system, software and its components are always a subject to exploitation because nothing is ever 100% perfect. If latest updates are not installed, the coding and design vulnerabilities in software applications and operating system are posing a risk of being abused by malware writers. Internet browsers, Adobe products, Sun Java, Windows Media Player, Apple Quicktime all have to be updated on regular basis.
Adobe products. Adobe Reader is usually installed with Speed launcher. This feature is loaded during Windows start-up thus prolonging the OS loading and storing the associated .exe file in Applications' folder where it may simply be another useless file which may be exploited during malware attack on the system. By reading this short article you can decide whether you really need this feature. More on Adobe Acrobat Reader related security issues here.
Adobe Flash is another subject to exploitation if not kept updated. Hackers are known to exploit Flash vulnerabilities which can lead to malware infection. When visiting a website that hosts a HTML page which requires a Flash script, users may encounter a malicious Flash redirector, or malicious script written to exploit vulnerability in the Flash Interpreter which causes it to execute automatically in order to infect the computer. Flash vulnerabilities are directly related to Web application and casual online gaming security. More extensive overview on this subject can be found here.

Java, if not kept updated, is the most common way of infecting computer with trojans while browser is rendering a HTML code at some dodgy adult or software cracking tools' website. It must be noted that most exploited vulnerability on such an occasion is previous Java version that has not been uninstalled after the new, updated one has been downloaded and installed. You can check whether you have two Java versions in your Windows pc by going to Control Panel and opening Add/Remove Programs. If you do have two Java updates listed, it is recommended that you uninstall the older one. You can check your system's Java status here.

2. Javascript enabled for all sites.

Regardless of the Web browser you are using, a Javascript can make your system less secure if enabled to run on all sites. The safe way of using Javascript is to enable it exclusively for trusted sites. Javascript is often the cause of malicious redirects to a site with either a malicious content or an intent to boost the incoming traffic.

3. Online game servers.

Because of the design of the online game architecture, firewalls and anti-malware software sometimes can't detect intrusions. That provides an opportunity for hackers to abuse the victim's machine by using online bots and rootkit-like techniques. More info on data and computer security threats related to online gaming can be found here.

4. Torrent, P2P (Peer-to-Peer) networks, File Sharing programs.

Connection to these networks is making the system susceptible to remote attacks and probability of downloading infected, malicious files. That in turn can lead to identity thefts. Malicious worms, backdoor Trojans, IRCBots and rootkits spread across P2P file sharing networks, gaming, dodgy adult and underground sites.

5. Infected files on USB and other storage media.

An Autorun.inf file can cause much trouble. More about this threat and how to avoid it you can read here.

6. Clicking unsolicited links in e-mail and Instant Messenger chats.

For more info as to why such links are being sent and what consequences such actions can have please see my previous posts here and here.

7. Rogue antivirus / antimalware software.

This includes clicking on pop-ups or banners that claim your computer is infected. All about rogues you can read in one of my previous posts here.

8. Backing up infected files.

A logical cause of re-infection.

9. Assuming that antivirus and/or firewall are not needed, or that they are providing 100% protection.

Two extreme assumptions that both can result in computer not being protected against cyber threats. On the first occasion, it is most likely that such a computer's owner won't even get that far as to visit this website to read this article, therefore, I am going to address the second assumption by saying that even protected machines get infected. Otherwise malware writers wouldn't waste their time on doing what they do. Here is an excerpt from Ivizsecurity.com blog:

Security products like anti-virus, firewalls, IDS/IPS and VPN have become of paramount importance to provide highest degree of confidentiality, availability and Integrity (CIA) to individuals and organizations. However, it is foolish to assume that security products are free from any vulnerability (security flaws). Security Products can also be of target of attacks from the attackers.

  By assuming that Anti-virus and Firewall will do the trick of fully protecting the machine, we risk to return to the beginning of this list, e.g. unpatched security holes.

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Data security news from Darkreading.com

Free anti malware tools from Emsisoft

There is a variety of malicious software removal tools available from Emsisoft for both, regular and advanced users.

Emsisoft Anti-Malware

For regular users the Anti-Malware software would be most suitable. It is available for download as a full free trial version for 30 days. After that time period in case the license is not renewed it switches to freeware version. Here is the list of features available in full version of Emsisoft Anti-Malware 6.0:

• File Guard that works as a real-time shield and compares every file downloaded to known malware patterns;
• dual scan engine consisting of: E1/A2 Emsisoft Anti-Malware engine, and E2/IK Ikarus Anti-Virus engine: a combination that works as 2 in 1. Available also in freeware mode.
• Behaviour Blocker: constantly monitors the behavior of all active programs and raises an alarm as soon as something suspicious happens. Works without the need for malware signatures as it is designed to be a part of so called zero-day protection capable of recognizing malicious actions performed by hijackers, trojans, keyloggers, spyware, adware, viruses, rootkits and worms by detecting their malicious behaviour in system;
• Updates can be set to be downloaded as often as 5 times a day;
• HiJack Free, an integrated system analysis tool designed for professionals to monitor autorun and running processes, services, port configuration, installed ActiveX objects (can be submitted for online analysis), LS Protocols. Advanced user's feature, available also in freeware mode;
• Commandline scanner. Also an advanced user's feature. A scanner without GUI.

If you want to perform just a quick check on your system, there are two available options that allow you to do just that: Web Malware scanner and MalAware, cloud and signature based light-weight freeware online scanner. Click here and proceed to Freeware section to perform a quick scan on your machine.

Emsisoft Emergency Kit is also available from the Freeware section at publisher's website. It is a very convenient tool to be kept on your USB stick in case your system fails to load the OS because of a virus or other malware. This is really more of an advanced user / admin type of software as it contains Commandline scanner which is supposed to be run from the command prompt; a HiJackFree tool (see the description for Anti-Malware above); and BlitzBlank, a tool that requires more advanced knowledge of Windows Operating System as it lets you delete malicious objects at boot time by using scripts. It is useful for removing locked files, destroying Windows Registry entries, disabling Windows drivers.

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Bot, Spybot and free malware removal

What are bots and Botnets?

By definition bot is a software application running automated tasks over the Internet like, for example, those best friends of SEO specialists: Google and Bing robot spiders/crawlers that index webpages. We however will be talking the removing of those bots that by About.com's definition are

type of malware which allows an attacker to gain complete control over the affected computer. Computers that are infected with a 'bot' are generally referred to as 'zombies'.

Description of botnets by Securelist.com website pretty much sums up the answer to questions like, what is a purpose of developing botnets and why would anyone want to create trojan bots:

Special Trojans – ‘bots’ (from “robot”) are created for this kind of networks, centrally managed by the remote “master”. The Trojan intrudes into thousands, tens of thousands or even millions of computers. This enables the master of the “zombie network” (or “bot-network”) to access resources of all infected computers and use them to own benefits. Sometimes such networks of “zombie-machines” come into the black Internet-market where they are acquired by spammers or rented.

The following video by rynesandbergfan23 explains what malicious bots are capable of, what to look out for and how to secure your machine so that its chances of getting infected are greatly reduced. (Note: if you haven't got a software to monitor your network connections similar to one shown in the video, you can use Command Prompt (Start-->Run-->cmd) instead. For the list of network connections and associated software applications maintaining them, type netstat -b in the Command Prompt and hit Enter):

Spybot

Last year my machine, despite the full ZoneAlarm's protection it had, got infected with what was known as Google Redirector malware. That's how I got familiar with a freeware called Spybot S&D (or Spybot Search&Destroy), a software project that financially depends on PayPal donations. This freeware is able to identify more than 820,000 pests (including Win32/Zbot (also known as ZeuS), SpyEye and TDSS trojans) by basically doing what it calls a bot-check. The following video will show you what features Spybot has got as well as how to scan and clean your machine:

Now, from my experience, Spybot is very useful to get rid of spyware, adware and all kinds of sneaky pests but it cannot serve as a replacement for an anti-virus software. Handling of malicious Windows Registry entries is one thing Spybot is really good at. The picture that follows is a screenshot of Spybot's scan results:

If you click on it and take a closer look, you can see that (apart from 2 DoubleClick tracking cookies) there are only 3 objects expanded that are not Registry entries.

Malware and spyware removal method

Let's get back to the video at this point. The author of the video comes up with what I see as a generally good idea as to how a Windows machine has to be cleaned: if one malware detection software comes up with detected objects after the scan, it is recommended that after deleting those objects, a system scan is run again, this time by using the same type of software by different vendor. In the video the free Malwarebytes Anti-Malware (appears to be most trusted free malware detector for Windows environment) scanner is used to compare scan results however, unlike that of the video author, our point here is not to demonstrate a comparison because no software is absolutely perfect. The point is using what Hitman Pro (also used in the video) developers call a 'second opinion'. Now, lets see what I've got after following this sequence: free Emsisoft Anti-Malware (Scan settings: Scan type: Deep Scan Objects: Rootkits, Memory, Traces, C:\ Scan archives: On ADS Scan: On) -->Spybot scan --> free Malwarebytes Anti-Malware (Deep Scan) --> Hitman Pro (Default scan):

• Emsisoft Anti-Malware detects 387 objects each related to one of the following: mywebsearch toolbar, zwinky toolbar, funwebproducts, Trojan.Win32.AddUser and Trojan-Downloader.Agent.  (No screenshot provided because of the amount of objects found yet the scan Report can be viewed by clicking here.)
• Spybot detects some MyWebSearch and FunWebProducts Windows Registry entries as seen in the screenshot above (the scan takes up to several hours)
• Malwarebytes Anti-malware still detects some MyWebSearch entries in Windows Registry and a Start Menu Hijack:

• Hitman Pro detects one remnant of malware in Windows Registry:

• Now the machine can be considered free of both, malware and spyware. Remember, before you start cleaning your machine, make sure you have:
• downloaded all the latest updates for the software you are going to use. If this doesn't work, the best thing to do is to obtain anti-malware software installation using other computer. Spybot for instance can be installed and run without the connection to Internet: latest updates is an optional step during the installation;
• disconnected the machine from the network either by removing cable or disabling/removing your wireless adapter. This is actually the first thing you want to do if you suspect your computer has been infected and you seem to have no control over running processes.

But speaking of Google Redirector... The only free tool that got rid of it was HitMan Pro (Google redirection infection is known as TDL3/TDL4 rootkit).  Mind you, that was back in May 2011, and as we know, things constantly change.

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How a banking trojan can steal your data and money

A quick look at Zbot

There are many ways hackers can try to steal personal data from computers. We will take a look at what is known as Zeus to give you the idea of how your banking information can be stolen, so that you know what to be aware of, and how to avoid of becoming a victim.

There is an in-depth analysis of ZeuS Banking trojan to be found at SecureWorks website by authors Kevin Stevens and Don Jackson, Security Researchers from SecureWorks Counter Threat Unit SM (CTU). While it is suggested that you read the whole article, I will post some excerpts here:

ZeuS is a well-known banking Trojan horse program, also known as crimeware. This trojan steals data from infected computers via web browsers and protected storage. Once infected, the computer sends the stolen data to a bot command and control (C&C) server, where the data is stored. ZeuS has evolved over time and includes a full arsenal of information stealing capabilities:

• Steals data submitted in HTTP forms

• Steals account credentials stored in the Windows Protected Storage

• Steals client-side X.509 public key infrastructure (PKI) certificates

• Steals FTP and POP account credentials

• Steals/deletes HTTP and Flash cookies

• Modifies the HTML pages of target websites for information stealing purposes

• Redirects victims from target web pages to attacker controlled ones

• Takes screenshots and scrapes HTML from target sites

• Searches for and uploads files from the infected computer

• Modifies the local hosts file (%systemroot%\system32\drivers\etc\hosts)

• Downloads and executes arbitrary programs

• Deletes crucial registry keys, rendering the computer unable to boot into Windows
•  

How to detect the ZeuS Banking Trojan on your computer
Computers infected with this version of ZeuS will have the following files and folders installed. The location depends on whether the victim has Administrator rights. The files will most likely have the HIDDEN attribute set to hide them from casual inspection.
With Administrator rights: 

%systemroot%\system32\sdra64.exe (malware)%systemroot%\system32\lowsec%systemroot%\system32\lowsec\user.ds (encrypted stolen data file) %systemroot%\system32\lowsec\user.ds.lll (temporary file for stolen data) %systemroot%\system32\lowsec\local.ds (encrypted configuration file)
Without Administrator rights: 

%appdata%\sdra64.exe%appdata%\lowsec%appdata%\lowsec\user.ds%appdata%\lowsec\user.ds.lll%appdata%\lowsec\local.ds 

ZeuS also makes registry changes to ensure that it starts up with Administrator privileges:
HKLM\Software\Microsoft\Windows NT\CurrentVersion\WinlogonFrom:"Userinit" = "C:\WINDOWS\system32\userinit.exe"To:"Userinit" = "C:\WINDOWS\system32\userinit.exe,C:\WINDOWS\system32\sdra64.exe"
Without Administrator rights:
HKCU\Software\Microsoft\Windows\CurrentVersion\RunAdd:"Userinit" = "C:\Documents and Settings\<user>\Application Data\sdra64.exe" 

The sdra64.exe program uses process injection to hide its presence in the list of running processes. Upon startup, it will inject code into winlogon.exe (if Administrator rights available) or explorer.exe (for non-Administrators) and exit. The injected code infects other processes to perform its data theft capabilities.

How your system can get infected

There is a list of ways your system can get infected to be found in one of my other posts here. Things you really should watch out for, and avoid, are emails supposedly sent from your bank where you are asked to follow a certain link in order to update your security details, or to download a file attached to the e-mail message. Here are few samples of such e-mail messages:

Dear Customer,
We detected irregular activity on your
Internet banking account.
For your protection, you must verify this
activity before you can continue using your
account.
Please download the document attached to this
email to review your account activity.
We will review the activity on your account
with you and upon verification, we will remove any restrictions placed on
your account.
If you choose to ignore our request, you leave us no choice
but to temporary suspend your account.
We ask that you allow at least 72 hours for the case to be
investigated and we strongly recommend to verify your
account in that time.
© Copyright Barclays Bank Holdings plc 2012 - All rights reserved

and

Dear Valued Customer,
Your account is suspended due to the number of incorrect login attempts.
For your protection, we've suspended your account .
To reactivate your account please download the document attached to this
e-mail and review your account activity.
If not completed until February 09, we will be forced to close your account .
Note: If you received these e-mail in your BULK/SPAM section please
add to your address book [e-mail address withdrawn]

Thank you,

Customer Support Service.

Copyright © NatWest Bank Plc. Limited. All rights reserved.

On both occasions senders obviously have made an opportunistic attempt to get me into downloading their malicious HTML files attached to messages without knowing that I'm not a customer of either of aforementioned banks.
So, what would have happened if I'd downloaded the attached file? I would most likely have infected my machine with a trojan bot spyware that would be capable of sending data from my computer to a remote server on the Internet, controlled by a cyber criminal, and basically making my machine a part of a botnet.
Or, if there would have been a link to follow, then, by clicking it, I would most likely have ended up on some bogus website designed by a cyber criminal for malicious purposes such as pharming (URL redirections with purpose of information stealing) or spreading malware infections. Example of a phishing message:

Dear Valued Customer,
our security filter noticed a malicious activity in your online account.
We were able to trace it to an unknown link thereby, placing
your online banking on suspension till this is resolved.
We implore you to go over your account details so
as to continue with your online transactions.
Click here to resolve the problem. [Link withdrawn]

Thank you for helping us to render you a maximum protection.

Security Department.

Alliance-leicester online banking.

Things to keep in mind

Regardless of the content of the message, remember: banks will not ask you for any security details or security updates via e-mail. Don't just click on links in emails you receive from someone. Make sure the sender is trusted and genuine, and the link does not look dodgy. (The same applies to Instant Messenger chats.) If you receive a suspicious email supposedly sent from your bank, and you are asked to proceed with giving away any of your personal or financial details, or to download an attachment, don't. Instead, forward the email message to the bank. Almost on all occasions you can find e-mail address for forwarding phishing emails to at the bank's official website. For more detailed information on types of scams related to Online banking, and to get a genuine advice, please visit Bank Safe Online, a website developed by UK Payments Administration Ltd.

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