Wikipedia:Reference desk/Archives/Computing/2010 August 12

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August 12

Getting the Images

How can one retrieve images etc. that have been taken off Internet just a few days ago. Taken off too early for archive.org and too late for google's cache -- Jon Ascton  (talk) 02:22, 12 August 2010 (UTC)

In general, unless you saved a copy yourself, it is not possible to retrieve data from a server after the server makes it unavailable. In some cases, a public service like Google.com or Archive.org will make copies available to the public, but it is not feasible for these services to realistically mirror every instant of every web-accessible server. In brief, "not possible," sorry. Nimur (talk) 02:30, 12 August 2010 (UTC)

Oh, come on, man ! Don't be so pessimistic. I am sure some guru's gonna along with a solution...

No, Nimur is correct. Archive.org and the Web page caching of Google and other search engines are remarkable resources, but they are not all-powerful. What I would try is other search engines' caches of the page; you might get lucky. Comet Tuttle (talk) 05:20, 12 August 2010 (UTC)

However, if you haven't done much web-surfing with the same machine since then, the images might still be in your browser's web-cache. We need to know what browser and what operating system you are using to help you recover them. CS Miller (talk) 10:13, 12 August 2010 (UTC)

Which Search Engine's Cache retains the oldest ?

Encrypting the contents of a folder

How do I secure the entire contents of a folder in Windows in such a way that someone without the password cannot even recognise what the content is? By that I mean that they should not even be able to tell that the file is for example a spreadsheet - instead of "secrettakeoverplan.xls" it should look like "nothingtoseehere.not". A multi-user setup won't work because that does not actually scramble and hide the content of other users' files. Roger (talk) 05:46, 12 August 2010 (UTC)

Since you say user access controls aren't good enough, you must be envisioning an attacker with administrative privileges or physical access to the hard drive or something of that sort. In that case, it's pretty hard to achieve what you're asking (impossible in general). It depends on what capabilities your attacker is supposed to have. One thing you could try is putting your sensitive files in a TrueCrypt container. But anyone with administrative privileges can read and write a TrueCrypt volume while it's mounted; for that matter, an administrator could load a kernel module that stole the volume's encryption keys, or logged your keystrokes. Even if the TrueCrypt volume isn't compromised, Excel will probably leave traces of the name and contents of your spreadsheet in the registry and the temporary folder. If you can be more specific about your threat model, it might be easier to help. -- BenRG (talk) 06:21, 12 August 2010 (UTC)

The threat isn't really a spy with cracking tools, its more likely to be a curious temp secretary browsing while I'm out with a client or the computer shop techie trawling customers' drives for porn while fixing or upgrading the pc (been there, done that!). I can't risk them finding trade secrets or client information. I used to simply store such files in a password protected zip file, but since XP, zip files are treated as "normal" folders and the old Winzip password protection no longer exists. Having to keep these files on a flash stick on my keyring is driving me nuts, I'd really like to be able to keep them securely on the PC's main drive. Roger (talk) 07:16, 12 August 2010 (UTC)

The best way of doing it is to use Unix-style commands; they're much more suitable for this sort of thing. So download Cygwin (AKA Unix-for-windows). Then cd to the directory just above the one you want (say it's called "foo") and run the following:

tar cvf foo.tar foo

gpg -c foo.tar

This will prompt you for a password. Then (after backing up!) do

shred foo/*

/bin/rm -rf foo

which will remove the whole directory. Now when you want to look at the stuff again,

gpg foo.tar.gpg

which will prompt you for the password, and then

tar xvf foo.tar

Hope this helps! --Trovatore (talk) 07:30, 12 August 2010 (UTC)

Well, it depends how paranoid you are. Here's what you can be sure of: if you have a secure computer, you encrypt something on it properly, and it goes to the tech shop, you can be assured that they can't read it. Travatore's solution is that using GPG (although there are easier ways to do it entirely in windows without messing with cygwin).

The problem is when you get the computer back, you log in and unencrypt the contents to use them. At the point you type the password into the computer that was in someone else's hands, it's possible for the computer to "phone home" the key to the tech shop. Then they can read it. This is called the "evil maid" scenario.

As you'll notice the vulnerability isn't the encryption, it's the fact that you could later inadvertently reveal your password. As for doing the encryption right, Truecrypt's good, PGP or it's Linux equivalent GPG are good, as is FreeOTFE. Actually the newer zip specifications are better than they were.

Finally ask yourself this: why are you bringing in your files to the tech shop in the first place? Is it you suspect your computer got a virus? If that's the case then the virus writer could do the same evil maid scenario as the tech shop guy could. What you're asking for isn't impossible, but you just need to be aware of the possible avenues of attack. Let us know if you'd like more specificity about any of those. This discussion could encompass a small text-book. Shadowjams (talk) 07:40, 12 August 2010 (UTC)

TrueCrypt is super easy to use and is very powerful. It basically creates little encrypted drives of arbitrary size. For your threat level it seems ideal in terms of protection and ease of use. As with any security regime there are always potential loopholes, but from what you've described, it'll certainly get around people casually stumbling across the data or poking around when it is under repair and so forth. It won't necessarily stop a dedicated ninja spy who has installed crazy malware on your computer and is also spying on you with cameras, but for practical use, it's pretty good, and straightforward. Much easier than playing around with Unix shell commands. When you ask people on here about cryptography, they always respond, like good security-minded people, with all sorts of worst case scenarios. If you listened to all of those you'd keep your offices lined with barbed wire and follow every employee home at night... or just do all the work yourself, in your barbed-wire office! Finding the reasonable compromise based on your own idea of what is at stake is obviously the only sane approach. --Mr.98 (talk) 12:37, 12 August 2010 (UTC)

I'll try out Truecrypt - I'm not responsible for nuclear missile security so the spy threat scenario is unrealistic. All I need is to keep financial and client info out of reach of the casual/incidental snoop. (The digital equivalent of a locked filing cabinet and a paper shredder) I just find having to use a flash stick tedious. Roger (talk) 13:38, 12 August 2010 (UTC)

Horrifically, nuclear missile security has actually far less in the past than the security many businesses apply to their tax information. The unlock code for the US Minuteman missiles during the Cold War was "00000000". "I've got the same combination on my luggage!". --Mr.98 (talk) 14:15, 12 August 2010 (UTC)

Regardless of the actual combination, they would probably keep the locks at 00000000 to allow the combination to be dialed in when necessary with a minimum of thought. Without any independent corroboration, I just don't believe that guy's story. Anyway, that combination lock was just one of many safeguards, unlike a TrueCrypt volume's passphrase, which is the only safeguard. -- BenRG (talk) 21:29, 12 August 2010 (UTC)

Keep in mind that the command centers for missiles are guarded by soldiers; their computer networks are not connected to the outside world; so it's irrelevant to discuss the "password strength" without a full run-down of other, complementary security measures. Cryptographically strong "secure" communication is important for missile command centers, but they also have policies regarding actual security, you know? Saying that the unlock-code is 00000 is tantamount to saying that certain interior doorways in the command-center are left unlocked; they are within a defended perimeter, and don't need to be locked. In computer-security, we ironically call this a demilitarized zone - the region where you are certain that additional security measures are unnecessary, because you have sufficiently isolated threats. Nimur (talk) 22:33, 12 August 2010 (UTC)

A TrueCrypt volume gives you the same level of secrecy as a removable flash drive, if you choose a strong passphrase and guard the passphrase as carefully as the flash drive. I don't recommend tar+gpg, since it's less convenient and there are more opportunities for leakage. -- BenRG (talk) 21:29, 12 August 2010 (UTC)

I respond with worst-case scenarios to make the point that you need to be specific about what you want to defend against. I'm not saying you should worry about keyloggers, I'm saying we can't make any recommendations until we know whether you are worried about keyloggers. -- BenRG (talk) 21:29, 12 August 2010 (UTC)

Thanks all, I now have a Truecrypt file on my PC and so far its meeting my requirement. Roger (talk) 18:19, 15 August 2010 (UTC)

"C" Language

Hello Friends,

Can anybody tell me the explanation about the following line?

  int i;
 i =23L;
 printf("%d %lu",i,i);

Why do we put 23L and what is the meaning? And give me one example code with output. —Preceding unsigned comment added by 122.164.62.13 (talk) 06:57, 12 August 2010 (UTC)

23L just indicates that 23 is a constant of type long. It's assigned to a variable of type int. Integers of different types are silently converted in C, so the "L" is pointless, but the assignment works. Then you have a line that prints the value (23) of i as an int and as an unsigned long. Since i is not an unsigned long, the result is undefined. Everything can happen. What will happen on the most common current computing environments is that the compiler will issue a warning, but the compiled program prints "23 23", since typically both int and unsigned long are 32 bits and have the same representation for small positive values. --Stephan Schulz (talk) 07:57, 12 August 2010 (UTC)

If the code had just said "i=23" instead of "i=23L", the program would have given exactly the same output. When you are writing your own programs, you'll just write "i=23" instead of "i=23L". The purpose of this exercise is to show the C compiler converting a long to an int on its own. Comet Tuttle (talk) 17:29, 12 August 2010 (UTC)

Leave USB pendrive stick in computer all the time?

How sensible would it be to leave a 2GB+ USB pendrive plugged into the back of my old WinXP computer all the time? I turn my computer on and off at least once a day. I would like to use the USB stick as a backup for my essential documents in case the HD suddenly goes kaput. Thanks 92.28.244.237 (talk) 10:32, 12 August 2010 (UTC)

Does the pen drive have any software on it? I know that because my computer's configured to boot from external disks, it tries to boot from my pen drive when I leave it in. If yours isn't, I don't think there should be too big an issue with it, but I'm no expert. sonia♫ 10:42, 12 August 2010 (UTC)

One possible problem is that if it 'sticks out' (depending on the design) it may be broken, and files lost, or damage the connector on the motherboard if jarred when the case is moved, cables are being attached/removed etc. If possible, I would attach it via a short USB cable, rather than directly to the socket. That way physical damage seems far less likely.

• If you are using it for backup then I would remove it from the PC. This way your Back-Up files are kept physically seperate from the Original files stored on the PC. Keeping Original and Back-Up together is bad practice. eg PC gets stolen USB likely goes with it. House fire, PC burns USB pendrive burns.
  
• In fact generally 2 backups would be advisable! One kept neaby for immediate access, another "Off-Site" so if original & Onsite Backup are lost, the Off-Site means that most of your files, less any recent changes, can be retrieved.
• See Backup for more information. 220.101 talk^\Contribs 12:08, 12 August 2010 (UTC)

My 2c; original and backup together is not always bad practice - you can always have a hard drive crash and the local backup comes in handy for quick restore. This practice is OK as long as you have an occasional offsite backup too; it's not always feasible or logistically possible to have frequent offsite backups (not everyone has fast or unlimited internet for example). Of course if you have a VERY important document that you cannot lose, you should onsite and offsite back it up every time it changes. Sandman30s (talk) 19:25, 12 August 2010 (UTC)

Note that even if it's a local backup, it doesn't mean it's a good idea to leave it connected all the time. If it's connected that mean it's at risk of malware (which no matter the OS, no matter how much you secure your computer or how careful you are, you should always consider a risk) and also means there's a slight risk of something like a highly catastrophic power supply failure taking it out along with your hard disk as well as similar stuff like catastrophic system file corruption resulting in your OS damaging both. (Presuming one is USB and one is SATA or whatever, then the risk of controller failure causing both to be damaged or corrupted shouldn't be a concern.) There's also a slightly higher risk of accidental deletion although with good practices you can reduce the chance you'll delete or overwrite both the backup and the original which should be what's of concern. If you let others use your computer and leave the backup drive connected, the risk of accidental deletion of both is likely to be higher. Malicious deletion may be as well, but realisticly, if you're worried about that then unless you lock your backup disk in a safe it's always going to be a concern.

In addition, even if you store it in your house, if you put it somewhere else you likely reduce the risk of it being stolen along with your computer. And it's sometimes recommended you have a folder with important documents in an easy to access location that you can hopefully grab in the event of fire (i.e. if you're home and it's safe), if you have such a thing, you can store your backup disk in it so you're more likely to be able to save it along with your computer.

Of course if you do happen to have a safe in your house, particularly a strong fireproof one then storing it in that hopefully reduces the risk (depending on how good the safe is and other factors) it will suffer whatever fate that may make you lose your computer hard disk (fire, theft, flood, house collapse, earthquake, tornado, tropical cyclone).

Nil Einne (talk) 23:01, 12 August 2010 (UTC)

Immediate termination

I'm looking for a Windows application that's like task manager, but allows you to kill programs immediately. I don't want a stupid confirmation window that asks whether I really want to end the task; I want a program that kills programs and frees up their memory by brute force, using whatever means necessary, as fast as possible. Actually, it would be better if the application let me press a hotkey, point to a window, click, and terminate whatever processes associated with the window, without opening up a window like Task Manager. Does anyone know of such an application? --99.237.234.104 (talk) 16:28, 12 August 2010 (UTC)

You have just described xkill. I'm sure you can find its Windows port somewhere.—Emil J. 16:45, 12 August 2010 (UTC)

You could install AutoHotkey and add this to your startup script:

   ^!Backspace::
       MouseGetPos,,,winid
       WinGet,pid,PID,ahk_id %winid%
       Process,Close,%pid%
       return

This will cause Ctrl+Alt+Backspace to immediately terminate the process that owns the window under the mouse cursor. With a little more effort I could make it change the cursor shape and then wait for a click, but you did say you didn't want any annoying confirmation steps. You can change the hotkey on the first line by using some combo of + (shift), ^ (ctrl), ! (alt), and # (win) followed by a key name; the details are in the help file. AutoHotkey has to be always running for this to work, but it's useful for a lot of other things and it uses very little RAM. -- BenRG (talk) 18:57, 12 August 2010 (UTC)

Facebook - contacting all those who Like a page

Resolved

I'm helping with my high school class' 25th reunion - sort of by default, since someone else had to move out of state. I'm trying to figure out if it's possible to contact all those who have clicked Like on the page - there are 126 out of 440 or so graduates. Or, is there even a way to find the names of all who Like the page? I figure that's a good way to get out the poll I'd like to do, as there are a few different options which I'd like to get peoples' opinions on; especially summer versus school year. (Our annual football rivalry, which is huge.)

I haven't been able to figure out a way, and Facebook's help center doens't seem that helpful; then again, I haven't been on Facebook very long, so maybe I'm missing something, but it seems like it's mostly just dozens of unanswered questions, with no technician I can ask. (Understandable, of course; I'm sure they'd be swamped if there was one. Or, maybe I'm just missing it.)

Enough people have written on the wall in the last year that I could just message them; they seem most interested, anyway. But, nobody's responded to the posts I've made on the wall, so I just wonder if they're even being read. And, I posted several polls 2 months ago, and they've gotten maybe 3-4 votes.

Or, maybe it's like one friend who just doens't have strong feelings either way.

Thanks for any help, and sorry if this isn't the right board, but I figure Facebook would be in with computers.Somebody or his brother (talk) 17:11, 12 August 2010 (UTC)

It's a bit tricky to find, but yes you can do this. Visit the page in question and click "Edit page" on the left hand side. On the new page that opens there is a link on the right hand side to "Send an update" which is to all people who like whatever that page is. Hope this helps! ZX81 ^talk 17:29, 12 August 2010 (UTC)

Thanks, I got it.Somebody or his brother (talk) 20:55, 12 August 2010 (UTC)

Fake Chase Bank Email

Hello,

I received an email from Chase Bank that looked legit. It said that Chase was going to deactivate my account, and to rectify the situation, I should follow the link they provided. I clicked the link, but once I saw the information it wanted from me, I became suspicious. I clicked one of the bottom links on the website called something like "Legal Information", which resulted in a pop-up saying something like "This is just demo. There is no legal information on the demo page". I contacted Chase Bank, as well as the Dean and Student Accounts of my college, since it mentioned my student accounts, (I was worried some other students might receive this email).

Is there anyone else I should contact? And because I opened the email, followed the link, and clicked "Legal Information", will I get a virus? Will the frauds be able to get any information off my computer, or from my email account?

Thank you for your help —Preceding unsigned comment added by 74.104.142.6 (talk) 23:05, 12 August 2010 (UTC)

It's probably a good idea to run a virus/spyware scan, but from what you've described, you're probably fine. Those scams are really about trying to capture your details (and you didn't give them anything) so if the scans come up negative then I wouldn't worry anymore about it.  ZX81  ^talk 01:07, 13 August 2010 (UTC)

These phishing e-mails are common. A few years ago, I received one claiming to come from a British bank, but actually linking to a website in Germany. I investigated and discovered the offending web pages in a directory attached to a personal website of an innocent party in Germany. I contacted both the bank and hosting company, and it was the small hosting company who reacted promptly in tracing the source of the fake pages to an anon IP and removing them within 24 hours of their appearance. I think the banks get so many of these fake sites that they haven't time to deal with them all. Dbfirs 09:49, 13 August 2010 (UTC)

Movie making software for beginner?

I'm looking for a movie making software for a beginner. It should give me more options than Windows Movie Maker but still easy to learn and use. Comparison of video editing software does not include how easy the software is to use so I would like some recommendations. thanks F (talk) 23:09, 12 August 2010 (UTC)

Sony Vegas is your best bet. Adobe Premiere is less intuitive to use, more expensive, and in my opinion, less powerful. The most complicated NLE I've ever used is Avid Media Composer.--Best Dog Ever (talk) 06:13, 13 August 2010 (UTC)

I've found Ulead Video Studio powerful and easy/intuitive to use. It also has a great DVD preview mode which is quite useful as it figures out beforehand how much space the compilation is going to take... I hate having to put the remaining 5% onto another DVD. Sandman30s (talk) 12:24, 13 August 2010 (UTC)