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Thursday, September 27, 2012

What are DDoS Attacks & How to Deal with them


The internet is abuzz with talks of the recent outage faced by Domain Registrar Godaddy. The outage was suspected to be because of a Distributed Denial of Service Attack (commonly known as a DDoS attack) that targeted Godaddy’s DNS servers, affecting several websites as well as email services. (However, a recent statement by Godaddy mentions that it was an internal network error that caused the interruption in services)
DDoS attacks are a fairly common occurrence on the internet and are something we’ve experienced in the past as well. Here is some more information on DDoS attacks, who they affect and how we mitigate such attacks.
What is a DDoS attack?
A Denial of Service attack aims to make a website unavailable to users by flooding the website’s servers with an extremely high number of requests. These multiple incoming requests can make website resolution exceedingly slow and can even cause servers to crash.
A Distributed Denial of Service (DDoS) attack is essentially a DoS attack that originates from multiple sources. Such attacks are usually carried out using thousands of unsuspecting zombie machines known as botnets.
DDoS attacks have traditionally been used by cyber criminals to extort money from website owners that rely on the accessibility of their websites. However ‘Hacktivists’ have also initiated such attacks in the past to bring down company and government websites in protest of certain policies or decisions.
A  popular recent example is anonymous’ attack in protest of the Megaupload Raids that targeted various government and music industry sites.
Who can it affect?
DDoS attacks are difficult to safeguard against completely and can affect large and small websites alike.
Having suffered a DDoS attack on our DNS servers in the past, we understand that such attacks can occur and the best solution is to have systems in place that allow you to mitigate the attack and get systems back online as soon as possible.
Which leads us to – How do we mitigate DDoS attacks?
While there isn’t a lot that can be done to prevent DDoS attacks, there are certain techniques that we employ to mitigate DDoS attacks and restore services.
To help mitigate DDoS attacks we’ve employed the services of Prolexic Technologies that is a global leader in DDoS Protection & Mitigation. While there are multiple ways in which Prolexic helps mitigate DDoS attacks, here is a simplified version of how Prolexic works.
  • BGP Routing:
    With BGP routing, when a DDoS attack occurs, our traffic gets routed through Prolexic’s servers where malicious and legitimate traffic is segregated and legitimate users can continue to access our services.
  • Advanced Filtering:
    As the traffic gets routed through Prolexic’s servers, their filtering technology identifies anomalies which are then “red flagged” by the system. Moreover, research is then conducted by Prolexic engineers to determine whether this activity should be blocked on the network. Once malicious activity has been determined, it is labeled in the system and blocked.
How can you independently mitigate attacks?
As a individual website owner you have limited control over a server but you can use CloudFlare to protect your websites from attacks.
CloudFlare protects your websites by routing traffic through their intelligent global network – a little like what Prolexic does for us :)
We already provide CloudFlare on our Hosting servers so Resellers can enable and start using it immediately. More information on how CloudFlare can protect you can be found here - http://www.cloudflare.com/overview
How Web Hosting Providers should deal with a DDoS Attack:
DDoS attacks are a very real threat to website owners and hosts worldwide but like I said before, there is no foolproof way for anyone to really protect themselves against such an attack.
As a Web Hosting provider yourself, I’m sure you’ve come across Customers that consider leaving you in the aftermath of a DDoS attack. You might have felt the same of your upstream provider as well. However, it’s important to remember that anyone can be a target.
An indicator of a good Host isn’t one that hasn’t been attacked yet but one that can effectively restore services and reduce damage.
How Web Hosts handle the situation is also an important indicator. I’ve always seen that the ones that do handle attacks effectively provide detailed information on the following: (This actually applies to most issues/interruption in services)
  1. Which services were affected?
  2. Are the services back up or how long will it take to restore services?
  3. Does the Client need to do anything?
  4. Why did this happen i.e. details of the DDoS attack
  5. How was the attack mitigated?
  6. Can this happen again?
  7. Who can Clients contact if they have any concerns?
Being honest and straightforward will go a long way in assuring your Customers that you’re doing everything you can to resolve the issue and they’ll respect you for keeping them in the loop.

So there you have it – everything you need to know about DDoS Attacks and how you can deal with them! I’d love to know what you think so do comment and let me know your thoughts.


Original Post

Friday, September 21, 2012

Windows Memory Dump

Windows Memory Dump


Hello Techies,

It is very often we see the blue screen on the Microsoft based OS.Basically we called this blue screen as 
Blue Screen Of Death (BSOD).





I have asked the question "what is BSOD" from many guys during the interviews but usually they replied
that it happened due to RAM or HDD failure, they simply reply that in this case they will replace either RAM or HDD to fix this issue on the server. 

So today i will give a idea about this BSOD and how to analyze this issue on windows platform.

->What is BSOD ?
->The Blue Screen of Death , displayed by the Microsoft Windows family of operating systems upon encountering a critical error,of a non-recoverable nature, that causes the system to crash.Stop errors are hardware or driver related, causing the computer to stop responding in order to prevent damage to the hardware or data.

->Type of memory dump ?
->There are three type of dumps created

1. Complete Memory Dump
2. Kernal Memory Dump
3. Small Memory Dump

1. Complete Memory Dump:-A Complete Memory Dump is the largest kernel-mode dump file. This file contains all the physical and virtual memory for the machine at the time of the fault.If you select the complete memory dump option, you must have a paging file on the boot volume The Complete Memory Dump file is written to %SystemRoot%\Memory.dmp by default.The Complete memory dump option is not available on computers that are running a 32-bit operating system and that having 2 gigabytes (GB) or more of RAM (by default).

2. Kernal Memory Dump:  A Kernel Memory Dump contains all the memory in use by the kernel at the time of the crash.The dump file will be around one-third the size of the physical memory on the system. This dump will not include unallocated memory or any memory allocated to applications. It only includes memory allocated to Windows kernel.The Kernel Memory Dump file is written to %SystemRoot%\Memory.dmp by (default)

3. Small Memory Dump:- A Small Memory Dump is much smaller than the other two crash dump files. It is exactly 64 KB in size (128KB on 64-bit systems) .This kind of dump file can be useful when space is greatly limited. However, it contains very less information for the reason of the crash.

                              How to enable memory dump on a windows server

Here i am going to configure the memory dump on Win-7/server 2008

1. Right click on my computer and click on properties then click on 2. Advance system setting option on left side ,then click on 3. Advance tab, Now click on 4. setting under Startup and recovery.Below are the screenshot






Same you can configure from the registery as well from the location as mentioned below

HKLM\System\CurrentControlSet\Control\CrashControl
All the things that you can configure via GUI can be configured via registery as well.

  • Write an event to the System Log checkbox = LogEvent
  • Automatically Restart checkbox = AutoReboot
  • Write Debugging Information drop-down = CrashDumpEnabled
  • Dump File text box = DumpFile
  • Overwrite any existing file checkbox = Overwrite 


                              How to Crash the server manually using keyboard

Now you have configured the memory dump on the server and now you can check as well if it is creating the memory dump file on the server or not.Also when you need to create memory dump file manually after a crash ,do the following to configure the same.

Using PS/2 keyboard :-


1. Start Registry Editor.
2. Locate the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parameters

3. On the Edit menu, click Add Value, and then add the following registry entry:

Name: CrashOnCtrlScroll
Data Type: REG_DWORD
Value: 1


4. Exit Registry Editor, and then restart the computer.


 Using USB keyboad:

1. Start Registry Editor.
2. Locate the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\kbdhid\Parameters

3. Make sure that the following registry entry is enabled:

Name: CrashOnCtrlScroll
Data Type: REG_DWORD
Value: 1


4. Exit Registry Editor.

If You can generate a system memory dump by holding down the right CTRL key and pressing the SCROLL LOCK key twice. (Ctrl+Scroll lock twice)

Note: Pressing left CTRL key does not generate the system memory dump.



Will come with new Blog shortly on How to Analyze the memory dump....... ;)

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