Dot Net Interview Questions

Friday, October 29, 2010

Question:-What do you mean by Share Point Portal ?
Answer: Here I have taken information regarding Share Point Portal Server 2003 provides mainly access to the crucial business information and applications. With the help of Share Point Server we can server information between Public Folders, Data Bases, File Servers and the websites that are based on Windows server 2003. This Share Point Portal is integrated with MSAccess and Windows servers, So we can get a Wide range of document management functionality. We can also create a full featured portal with readymade navigation and structure.

Question:-What is cross page posting in ASP.NET2.0 ?
Answer: When we have to post data from one page to another in application we used server.transfer method but in this the URL remains the same but in cross page posting there is little different there is normal post back is done but in target page we can access values of server control in the source page.This is quite simple we have to only set the PostBackUrl property of Button,LinkButton or imagebutton which specifies the target page. In target page we can access the PreviousPage property. and we have to use the @PreviousPageType directive. We can access control of PreviousPage by using the findcontrol method. When we set the PostBackURL property ASP.NET framework bind the HTML and Javascript function automatically.

Question: How to start Outlook,NotePad file in AsP.NET with code ?
Answer: Here is the syntax to open outlook or notepad file in ASP.NET VB.NET Process.Start("Notepad.exe") Process.Start("msimn.exe"); C#.NET System.Diagnostics.Process.Start("msimn.exe"); System.Diagnostics.Process.Start("Notepad.exe");

Question: What is the purpose of IIS ?
Answer: We can call IIS(Internet Information Services) a powerful Web server that helps us creating highly reliable, scalable and manageable infrastructure for Web application which runs on Windows Server 2003. IIS helps development center and increase Web site and application availability while lowering system administration costs. It also runs on Windows NT/2000 platforms and also for above versions. With IIS, Microsoft includes a set of programs for building and administering Web sites, a search engine, and support for writing Web-based applications that access database. IIS also called http server since it process the http request and gets http response.

Question: What is main difference between GridLayout and FormLayout ?
Answer: GridLayout helps in providing absolute positioning of every control placed on the page. It is easier to develop page with absolute positioning because control can be placed any where according to our requirement. But FormLayout is little different only experience Web Developer used this one reason is it is helpful for wider range browser. If there is absolute positioning we can notice that there are number of DIV tags. But in FormLayout whole work are done through the tables.

Question: How Visual SourceSafe helps Us ?
Answer: One of the powerful tool provided by Microsoft to keep up-to-date of files system its keeps records of file history once we add files to source safe it can be add to database and the changes ads by different user to this files are maintained in database from that we can get the older version of files to. This also helps in sharing,merging of files.

Question:-Can you define what is SharePoint and some overview about this ?
Answer: SharePoint helps workers for creating powerful personalized interfaces only by dragging and drop pre-defined Web Part Components. And these Web Parts components also helps non programmers to get information which care and customize the appearance of Web pages. To under stand it we take an example one Web Part might display a user's information another might create a graph showing current employee status and a third might show a list of Employees Salary. This is also possible that each functions has a link to a video or audio presentation. So now Developers are unable to create these Web Part components and make them available to SharePoint users.

Question:-What is different between WebUserControl and in WebCustomControl ?
Answer: Web user controls :- Web User Control is Easier to create and another thing is that its support is limited for users who use a visual design tool one good thing is that its contains static layout one more thing a separate copy is required for each application.
Web custom controls:-Web Custom Control is typical to create and good for dynamic layout and another thing is it have full tool support for user and a single copy of control is required because it is placed in Global Assembly cache.

Question:-What is Sandbox in SQL server and explain permission level in Sql Server ?
Answer: Sandbox is place where we run trused program or script which is created from the third party. There are three type of Sandbox where user code run.
Safe Access Sandbox:-Here we can only create stored procedure,triggers,functions,datatypes etc.But we doesnot have acess memory ,disk etc.
External Access Sandbox:-We cn access File systems outside the box. We can not play with threading,memory allocation etc.
Unsafe Access Sandbox:-Here we can write unreliable and unsafe code.

Question:-How many types of cookies are there in .NET ?
Answer: Two type of cookeies.
a) single valued eg request.cookies(”UserName”).value=”dotnetquestion”
b)Multivalued cookies. These are used in the way collections are used example
request.cookies(”CookiName”)(”UserName”)=”dotnetquestionMahesh”
request.cookies(”CookiName”)(”UserID”)=”interview″

Question: When we get Error 'HTTP 502 Proxy Error' ?
Answer: We get this error when we execute ASP.NET Web pages in Visual Web Developer Web server, because the URL randomly select port number and proxy servers did not recognize the URL and return this error. To resolve this problem we have to change settings in Internet Explorer to bypass the proxy server for local addresses, so that the request is not sent to the proxy.

Question:-What do you mean by three-tier architecture?
Answer: The three-tier architecture was comes into existence to improve management of code and contents and to improve the performance of the web based applications. There are mainly three layers in three-tier architecture. the are define as follows

(1)Presentation
(2)Business Logic

(3)Database

(1)First layer Presentation contains mainly the interface code, and this is shown to user. This code could contain any technology that can be used on the client side like HTML, JavaScript or VBScript etc.

(2)Second layer is Business Logic which contains all the code of the server-side .This layer have code to interact with database and to query, manipulate, pass data to user interface and handle any input from the UI as well.

(3)Third layer Data represents the data store like MS Access, SQL Server, an XML file, an Excel file or even a text file containing data also some additional database are also added to that layers.

Question: What is Finalizer in .NET define Dispose and Finalize?
Answer: We can say that Finalizer are the methods that's helps in cleanp the code that is executed before object is garbage collected .The process is called finalization . There are two methods of finalizer Dispose and Finalize .There is little diffrenet between two of this method .
When we call Dispose method is realse all the resources hold by an object as well as all the resorces hold by the parent object.When we call Dispose method it clean managed as well as unmanaged resources.
Finalize methd also cleans resources but finalize call dispose clears only the unmanged resources because in finalization the garbase collecter clears all the object hold by managed code so finalization fails to prevent thos one of methd is used that is: GC.SuppressFinalize.

Question: What is late binding ?
Answer: When code interacts with an object dynamically at runtime .because our code literally doesnot care what type of object it is interacting and with the methods thats are supported by object and with the methods thats are supported by object .The type of object is not known by the IDE or compiler ,no Intellisense nor compile-time syntax checking is possible but we get unprecedented flexibilty in exchange.if we enable strict type checking by using option strict on at the top of our code modules ,then IDE and compiler will enforce early binding behaviour .By default Late binding is done.

Question:-Does .NET CLR and SQL SERVER run in different process?
Answer: Dot Net CLR and all .net realtes application and Sql Server run in same process or we can say that that on the same address because there is no issue of speed because if these two process are run in different process then there may be a speed issue created one process goes fast and other slow may create the problem.

Question: The IHttpHandler and IHttpHandlerFactory interfaces ?
Answer: The IHttpHandler interface is implemented by all the handlers. The interface consists of one property called IsReusable. The IsReusable property gets a value indicating whether another request can use the IHttpHandler instance. The method ProcessRequest() allows you to process the current request. This is the core place where all your code goes. This method receives a parameter of type HttpContext using which you can access the intrinsic objects such as Request and Response. The IHttpHandlerFactory interface consists of two methods - GetHandler and ReleaseHandler. The GetHandler() method instantiates the required HTTP handler based on some condition and returns it back to ASP.NET. The ReleaseHandler() method allows the factory to reuse an existing handler.

Question: what is Viewstate?
Answer:View state is used by the ASP.NET page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.
State management is the process by which you maintain state and page information over multiple requests for the same or different pages.

Tracing a hacker

Wednesday, October 27, 2010

Sometimes, it's just not enough to simply know that there's a Trojan or Virus onboard. Sometimes you need to know exactly why that file is onboard, how it got there - but most importantly, who put it there.

By enumerating the attacker in the same way that they have enumerated the victim, you will be able to see the bigger picture and establish what you're up against. But how can you do this? Read on...

## Connections make the world go round ##

The computer world, at any rate. Every single time you open up a website, send an email or upload your webpages into cyberspace, you are connecting to another machine in order to get the job done. This, of course, presents a major problem, because this simple act is what allows malicious users to target a machine in the first place.

# How do these people find their victim?

Well, first of all, they need to get hold of the victim's IP Address. Your IP (Internet Protocol) address reveals your point of entry to the Internet and can be used in many ways to cause your online activities many, many problems. It may not reveal you by name, but it may be uniquely identifiable and it represents your digital ID while you are online (especially so if you're on a fixed IP / DSL etc).

With an IP address, a Hacker can find out all sorts of weird and wonderful things about their victim (as well as causing all kinds of other trouble, the biggest two being Portnukes/Trojans and the dreaded DoS ((Denial of Service)) attack). Some Hackers like to collect IP Addresses like badges, and like to go back to old targets, messing them around every so often. An IP address is incredibly easy to obtain - until recently, many realtime chat applications (such as MSN) were goldmines of information. Your IP Address is contained as part of the Header Code on all emails that you send and webpages that you visit can store all kinds of information about you. A common trick is for the Hacker to go into a Chatroom, paste his supposed website address all over the place, and when the unsuspecting victim visits, everything about your computer from the operating system to the screen resolution can be logged...and, of course, the all important IP address. In addition, a simple network-wide port scan will reveal vulnerable target machines, and a war-dialler will scan thousands of lines for exposed modems that the hacker can exploit.

So now that you know some of the basic dangers, you're probably wondering how these people connect to a victim's machine?

## Virtual and Physical Ports ##

Everything that you recieve over the Internet comes as a result of other machines connecting to your computer's ports. You have two types; Physical are the holes in the back of your machine, but the important ones are Virtual. These allow transfer of data between your computer and the outside world, some with allocated functions, some without, but knowing how these work is the first step to discovering who is attacking you; you simply MUST have a basic knowledge of this, or you won't get much further.

# What the phrases TCP/UDP actually mean

TCP/IP stands for Transmission Control Protocol and Internet Protocol, a TCP/IP packet is a block of data which is compressed, then a header is put on it and it is sent to another computer (UDP stands for User Datagram Protocol). This is how ALL internet transfers occur, by sending packets. The header in a packet contains the IP address of the one who originally sent you it. Now, your computer comes with an excellent (and free) tool that allows you to see anything that is connected (or is attempting to connect) to you, although bear in mind that it offers no blocking protection; it simply tells you what is going on, and that tool is NETSTAT.

## Netstat: Your first line of defence ##

Netstat is a very fast and reliable method of seeing exactly who or what is connected (or connecting) to your computer. Open up DOS (Start/Programs/MS-DOS Prompt on most systems), and in the MSDOS Prompt, type:

netstat -a

(make sure you include the space inbetween the "t" and the "a").

If you're connected to the Internet when you do this, you should see something like:

QUOTE

Active Connections Proto Local Address Foreign Address State TCP macintosh: 20034 modem-123.tun.dialup.co.uk: 50505 ESTABLISHED TCP macintosh: 80 proxy.webcache.eng.sq: 30101 TIME_WAIT TCP macintosh MACINTOSH: 0 LISTENING TCP macintosh MACINTOSH: 0 LISTENING TCP macintosh MACINTOSH: 0 LISTENING

Now, "Proto(col)" simply means what kind of data transmission is taking place (TCP or UDP), "Local address" is your computer (and the number next to it tells you what port you're connected on), "Foreign Address" is the machine that is connected to you (and what port they're using), and finally "State" is simply whether or not a connection is actually established, or whether the machine in question is waiting for a transmission, or timing out etc.

Now, you need to know all of Netstat's various commands, so type:

netstat ?

You will get something like this:

QUOTE

Displays protocol statistics and current TCP/IP network connections. NETSTAT [-a] [-e] [-n] [-s] [-p proto] [-r] [interval] -a Displays all connections and listening ports. -e Displays Ethernet statistics. This may be combined with the -s option. -n Displays addresses and port numbers in numerical form. -p proto Shows connections for the protocol specified by proto; proto may be TCP or UDP. If used with the -s option to display per-protocol statistics, proto may be TCP, UDP, or IP. -r Displays the routing table. -s Displays per-protocol statistics. By default, statistics are shown for TCP, UDP and IP; the -p option may be used to specify a subset of the default.

Have a play around with the various options, but the most important use of these methods is when you combine them. The best command to use is

netstat -an

because this will list all connections in Numerical Form, which makes it a lot easier to trace malicious users....Hostnames can be a little confusing if you don't know what you're doing (although they're easily understandable, as we shall see later). Also, by doing this, you can also find out what your own IP address is, which is always useful.

Also,

netstat -b

will tell you what ports are open and what programs are connecting to the internet.

## Types of Port ##

It would be impossible to find out who was attacking you if computers could just access any old port to perform an important function; how could you tell a mail transfer from a Trojan Attack? Well, good news, because your regular, normal connections are assigned to low, commonly used ports, and in general, the higher the number used, the more you should be suspicious. Here are the three main types of port:

# Well Known PortsThese run from 0 to 1023, and are bound to the common services that run on them (for example, mail runs on channel 25 tcp/udp, which is smtp (Simple Mail Transfer Protocol) so if you find one of these ports open (and you usually will), it's usually because of an essential function.

# Registered PortsThese run on 1024 to 49151. Although not bound to a particular service, these are normally used by networking utilities like FTP software, Email client and so on, and they do this by opening on a random port within this range before communicating with the remote server, so don't panic (just be wary, perhaps) if you see any of these open, because they usually close automatically when the system that's running on them terminates (for example, type in a common website name in your browser with netstat open, and watch as it opens up a port at random to act as a buffer for the remote servers). Services like MSN Messenger and ICQ usually run on these Ports.

# Dynamic/Private PortsRanging from 49152 to 65535, these things are rarely used except with certain programs, and even then not very often. This is indeed the usual range of the Trojan, so if you find any of these open, be very suspicious. So, just to recap:

QUOTE

Well Known Ports 0 to 1023 Commonly used, little danger. Registered Ports 1024 to 49151 Not as common, just be careful. Dynamic/Private Ports 49152 to 65535 Be extremely suspicious.

## The hunt is on ##

Now, it is essential that you know what you're looking for, and the most common way someone will attack your machine is with a Trojan. This is a program that is sent to you in an email, or attempts to bind itself to one of your ports, and when activated, it can give the user your passwords, access to your hard drive...they can even make your CD Tray pop open and shut. At the end of this Document, you will find a list of the most commonly used Trojans and the ports they operate on. For now, let's take another look at that first example of Netstat....

QUOTE

Active Connections Proto Local Address Foreign Address State TCP macintosh: 27374 modem-123.tun.dialup.co.uk: 50505 ESTABLISHED TCP macintosh: 80 proxy.webcache.eng.sq: 30101 TIME_WAIT TCP macintosh MACINTOSH: 0 LISTENING TCP macintosh MACINTOSH: 0 LISTENING TCP macintosh MACINTOSH: 0 LISTENING

Now, straight away, this should make more sense to you. Your computer is connected on two ports, 80 and 27374. Port 80 is used for http/www transmissions (ie for all intents and purposes, its how you connect to the net, although of course it's a lot more complicated than that). Port 27374, however, is distinctly suspicious; first of all, it is in the registered port range, and although other services (like MSN) use these, let's assume that you have nothing at all running like instant messengers, webpages etc....you're simply connected to the net through proxy. So, now this connection is looking even more troublesome, and when you realise that 27374 is a common port for Netbus (a potentially destructive Trojan), you can see that something is untoward here. So, what you would do is:

QUOTE

1) run Netstat , and use: Netstat -a then Netstat -an So you have both Hostnames AND IP addresses.

## Tracerouting ##

Having the attacker's IP is all well and good, but what can you do with it? The answer is, a lot more! It's not enough to have the address, you also need to know where the attacker's connections are coming from. You may have used automated tracerouting tools before, but do you jknow how they work?

Go back to MSDOS and type

QUOTE

tracert *type IP address/Hostname here*

Now, what happens is, the Traceroute will show you all the computers inbetween you and the target machine, including blockages, firewalls etc. More often than not, the hostname address listed before the final one will belong to the Hacker's ISP Company. It'll either say who the ISP is somewhere in there, or else you run a second trace on the new IP/hostname address to see who the ISP Company in question is. If the Hostname that you get back doesn't actually seem to mention an actual geographical location within its text, you may think all is lost. But fear not! Suppose you get a hostname such as

http://www.haha.com

Well, that tells us nothing, right? Wrong....simply enter the hostname in your browser, and though many times you will get nothing back, sometimes it will resolve to an ISP, and from there you can easily find out its location and in what areas they operate. This at least gives you a firm geographical location to carry out your investigations in.

If you STILL have nothing, as a last resort you COULD try connecting to your target's ISP's port 13 by Telnet, which will tell you how many hours ahead or behind this ISP is of GMT, thus giving you a geographical trace based on the time mentioned (although bear in mind, the ISP may be doing something stupid like not having their clocks set correctly, giving you a misleading trace. Similarly, a common tactic of Hackers is to deliberately have their computer's clock set to a totally wrong time, so as to throw you off the scent). Also, unless you know what you're doing, I wouldn't advise using Telnet (which is outside the parameters of this tutorial).

## Reverse DNS Query ##

This is probably the most effective way of running a trace on somebody. If ever you're in a chatroom and you see someone saying that they've "hacked into a satellite orbiting the Earth, and are taking pictures of your house right now", ignore them because that's just bad movie nonsense. THIS method is the way to go, with regard to finding out what country (even maybe what State/City etc) someone resides, although it's actually almost impossible to find an EXACT geographical location without actually breaking into your ISP's Head Office and running off with the safe.

To run an rDNS query, simply go back to MS-DOS and type

netstat

and hit return. Any active connections will resolve to hostnames rather than a numerical format.

# DNS

DNS stands for Domain Name Server. These are machines connected to the Internet whose job it is to keep track of the IP Addresses and Domain Names of other machines. When called upon, they take the ASCII Domain Name and convert it to the relevant numeric IP Address. A DNS search translates a hostname into an IP address....which is why we can enter "www.Hotmail.com" and get the website to come up, instead of having to actually remember Hotmail's IP address and enter that instead. Well, Reverse DNS, of course, translates the IP Address into a Hostname (ie - in letters and words instead of numbers, because sometimes the Hacker will employ various methods to stop Netstat from picking up a correct Hostname).

So, for example,

298.12.87.32 is NOT a Hostname.
mail6.bol.net.au IS a Hostname.

Anyway, see the section at the end? (au) means the target lives in Australia. Most (if not all) hostnames end in a specific Country Code, thus narrowing down your search even further. If you know your target's Email Address (ie they foolishly sent you a hate mail, but were silly enough to use a valid email address) but nothing else, then you can use the Country codes to deduce where they're from as well. You can also deduce the IP address of the sender by looking at the emails header (a "hidden" line of code which contains information on the sender)...on Hotmail for example, go to Preferences, and select the "Full Header's Visible" option. Alternatively, you can run a "Finger" Trace on the email address, at:

www.samspade.org

Plus, some ISP's include their name in your Email Address with them too (ie Wanadoo, Supanet etc), and your Hacker may be using an email account that's been provided by a Website hosting company, meaning this would probably have the website host's name in the email address (ie Webspawners). So, you could use the information gleaned to maybe even hunt down their website (then you could run a website check as mentioned previously) or report abuse of that Website Provider's Email account (and thus, the Website that it goes with) to

abuse@companynamegoeshere.com

If your Hacker happens to reside in the USA, go to:

www.usps.gov/ncsc/lookups/abbr_state.txt

for a complete list of US State abbreviatons.

## List of Ports commonly used by Trojans ##

Please note that this isn't a complete list by any means, but it will give you an idea of what to look out for in Netstat. Be aware that some of the lower Ports may well be running valid services.

UDP: 1349 Back Ofrice DLL
31337 BackOfrice 1.20
31338 DeepBO
54321 BackOfrice 2000


TCP: 21 Blade Runner, Doly Trojan, Fore, Invisible FTP, WebEx, WinCrash
23 Tiny Telnet Server
25 Antigen, Email Password Sender, Haebu Coceda, Shtrilitz Stealth, Terminator, WinPC, WinSpy, Kuang2 0.17A-0.30
31 Hackers Paradise
80 Executor
456 Hackers Paradise
555 Ini-Killer, Phase Zero, Stealth Spy
666 Satanz Backdoor
1001 Silencer, WebEx
1011 Doly Trojan
1170 Psyber Stream Server, Voice
1234 Ultors Trojan
1243 SubSeven 1.0 - 1.8
1245 VooDoo Doll
1492 FTP99CMP
1600 Shivka-Burka
1807 SpySender
1981 Shockrave
1999 BackDoor 1.00-1.03
2001 Trojan Cow
2023 Ripper
2115 Bugs
2140 Deep Throat, The Invasor
2801 Phineas Phucker
3024 WinCrash
3129 Masters Paradise
3150 Deep Throat, The Invasor
3700 Portal of Doom
4092 WinCrash
4567 File Nail 1
4590 ICQTrojan
5000 Bubbel
5000 Sockets de Troie
5001 Sockets de Troie
5321 Firehotcker
5400 Blade Runner 0.80 Alpha
5401 Blade Runner 0.80 Alpha
5402 Blade Runner 0.80 Alpha
5400 Blade Runner
5401 Blade Runner
5402 Blade Runner
5569 Robo-Hack
5742 WinCrash
6670 DeepThroat
6771 DeepThroat
6969 GateCrasher, Priority
7000 Remote Grab
7300 NetMonitor
7301 NetMonitor
7306 NetMonitor
7307 NetMonitor
7308 NetMonitor
7789 ICKiller
8787 BackOfrice 2000
9872 Portal of Doom
9873 Portal of Doom
9874 Portal of Doom
9875 Portal of Doom
9989 iNi-Killer
10067 Portal of Doom
10167 Portal of Doom
10607 Coma 1.0.9
11000 Senna Spy
11223 Progenic trojan
12223 Hack´99 KeyLogger
12345 GabanBus, NetBus
12346 GabanBus, NetBus
12361 Whack-a-mole
12362 Whack-a-mole
16969 Priority
20001 Millennium
20034 NetBus 2.0, Beta-NetBus 2.01
21544 GirlFriend 1.0, Beta-1.35
22222 Prosiak
23456 Evil FTP, Ugly FTP
26274 Delta
30100 NetSphere 1.27a
30101 NetSphere 1.27a
30102 NetSphere 1.27a
31337 Back Orifice
31338 Back Orifice, DeepBO
31339 NetSpy DK
31666 BOWhack
33333 Prosiak
34324 BigGluck, TN
40412 The Spy
40421 Masters Paradise
40422 Masters Paradise
40423 Masters Paradise
40426 Masters Paradise
47262 Delta
50505 Sockets de Troie
50766 Fore
53001 Remote Windows Shutdown
54321 SchoolBus .69-1.11
61466 Telecommando
65000 Devil