How a cracker can run malicious code on the user’s computer.

Posted on 2006-04-20
Last Modified: 2012-05-05
How a cracker can run malicious code on the user’s computer.
Question by:teera

    Assisted Solution

    mmm, this is a question that does not really have a short answer. It really depends on so many things, like the Operating system that the attacking machine is running, the hardware that the target machine is running (sometimes) and the additional applications that are installed.

    The simplified answer is...

    Remote code execution is possible due to bugs in software, the more software installed, the more possiblity of bugs existing and therefore the more chance of running code on a users machine. Code can also be run on a users machine by them simply excpeting a file and running it!

    Simple precautions can be taken to reduce the chance of malicious code being run, but it is nearly never possible to make it impossible.

    Can you be more specific about your question? Then I can be more specific with the answer. Are you concerned about your security? On a home machine, or a web server etc?

    LVL 20

    Assisted Solution

    Usually this is accomplished by buffer overflow. Like expert-ad said, this is usually only doable in poorly written software. Basically, a program tries to put more information into the buffer than there is actual memory. The information that overflows ends up into the memory locations next to it, creating the intrusion method. From there, the attacker may use that buffer for just about anything, though its usually malicious code in the form of a backdoor or virus/spyware.

    Buffer overflows may cause a process to crash or produce incorrect results. They can be triggered by inputs specifically designed to execute malicious code or to make the program operate in an unintended way. As such, buffer overflows cause many software vulnerabilities and form the basis of many exploits. Sufficient bounds checking by either the programmer or the compiler can prevent buffer overflows.

    LVL 51

    Expert Comment

    by:Keith Alabaster
    Dvation gives a good account here.

    LVL 38

    Accepted Solution

    There are numerous vectors, phishing and malicious site's are popping up more and more, and using ActiveX controls, or image processing exploits for example a "cracker" may obtain information without having to do much at all except trick you into visiting their web-site
    Phishers use URL spoofing, like the IDN spoofs (mozilla/firefox test)
    or simple html "misdirection" <a href=>Http://<./a> If you make your website look like the site the user thinks they are going to you may trick them into giving you their bank account username password, for just about anything...

    Then there was the M$ WMF image exploit, that affected all M$ OS's, even Vista (their most secure OS?)
    I'm actually surprized that this one hasn't happened yet, erasing your HD through an activeX control in IE:

    There are other ways, such as email attachments, or even preview pane (in outlook) execution (like the wmf images) exploits. Typically best practices will mitigate what a virus or malicious program can do:
    However in the WMF case the code executes as SYSTEM, no matter what security group the user belongs to.

    Not limited to "evil" hackers...
    You could also be like sony, and assume (correctly) that 95% of windows users don't follow best practices, and run as admin for day to day activites, and as such, sony put a rootkit on a few cd's that tried to keep you from making unauthorized copies of those CD's. The rootkit did not work on anyother OS, but there was another rootkit that did sort of work on MAC's.

    Then there are the old stand-by's, exloiting a poorly secured install of IIS, or a user having open ports and file shares...
    LVL 24

    Assisted Solution

    Open up a few different file systems and make them available to anyone unsecured (eg the microsoft way). Advertise as desired. Don't use a firewall or update any product, and ensure you've loaded up, stocked up well on microsoft products.

    Sit back, wait and watch, and welcome the crackers who'll compete with each other for your system
    LVL 24

    Expert Comment

    er, we cannot go and teach you how to be a cracker yourself, not at any price (or amount of points)
    LVL 10

    Assisted Solution

    Take a look at and click on "Vulnerabilities". You can see a lot of ways crackers/hackers/etc can get into a system.

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    Highfive + Dolby Voice = No More Audio Complaints!

    Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

    Suggested Solutions

    This story has been written with permission from the scammed victim, a valued client of mine – identity protected by request.
    Healthcare organizations in the United States must adhere to the guidance of both the HIPAA (Health Insurance Portability and Accountability Act) and HITECH (Health Information Technology for Economic and Clinical Health Act) for securing and protec…
    Sending a Secure fax is easy with eFax Corporate ( First, Just open a new email message.  In the To field, type your recipient's fax number You can even send a secure international fax — just include t…
    Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…

    759 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    14 Experts available now in Live!

    Get 1:1 Help Now