Wikipedia:Reference desk/Archives/Computing/2014 March 16

Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 16

can spammers see that i opened their email

i get 10+ spam messages a day on my old hotmail e-mail, mainly false dating/porn-related emails. do the spammers get notifications that i opened their email? i assume no. also, there's no way that an e-mail can be malicious today, right? HTML standards and the use of add-ons such as noscript should eliminate the chance of malicious e-mails.Bananas99 (talk) 02:49, 16 March 2014 (UTC)

One trick they use is to embed within the message a small image (1 pixel by 1 pixel, for example), whose URL contains a unique number. If that picture is downloaded, they know that you opened the message. Many e-mail clients allow you to turn off automatic image downloads from unfamiliar addresses. —Nelson Ricardo (talk) 03:24, 16 March 2014 (UTC)

• For services like Gmail unique image id as described by User:Nricardo is blocked (Gmail either copies images to their server — their newest implementation, else they will not show images, you will have an option "Display image below"). Most probably Yahoo has similar security. Another thing: do not click on links in such emails. Tito☸Dutta 04:12, 16 March 2014 (UTC)

Actually I have a question about this. I knew about the image tracking trick, but how does Gmail do their new trick where they copy images to their server and then show you them anyway? Surely the unique ID attached to the image means the sender is only tracking whether the image with that ID has been opened. It would make no difference to them whether that is done by the end user or by a server along the way... so what am I missing? —Noiratsi (talk) 07:43, 16 March 2014 (UTC)

This way, the HTTP request from Google makes more work for the spammer's server while telling them only that Google has received the message, not that some human has read it. —Tamfang (talk) 17:25, 16 March 2014 (UTC)

That still tells the spammers that the e-mail address exists, but does not tell them that it is actually being used, or that the owner is interested in their spam. But even that information could encourage spammers to send more spam. JIP | Talk 18:39, 16 March 2014 (UTC)

If your browser fetches the image, the web server's owner can do IP geolocation and reverse IP lookup on you. Open an email while at work, and now some loonie knows where you work, or they'll know roughly where you live. More about privacy than spam. (And I see the ha-ha of writing this with my IP address clearly visible to one and all.) 88.112.50.121 (talk) 00:09, 17 March 2014 (UTC)

About Interview

Are technical questions asked in " Personal Interview" for a position like Assistant Manager for Information Technology for who have qualified in a first round written examination with multiple choice type questions on technical aspects of Information Technology and other topics like reasoning math general knowledge etc asked.The company concerned is an electricity generation company.What do the interviewers try to asses and how they do in this type of Personal Interview.117.194.228.17 (talk) 08:32, 16 March 2014 (UTC)

For positions like these, competence in the English language is required, if the job is in an English-speaking country.

You could gain such competence by taking a course of a few years in an English-speaking country.

Hope this helps! --Demiurge1000 (talk) 08:40, 16 March 2014 (UTC)

Typically, only minimal mathematical skills are needed for IT positions. By that I mean addition, subtraction, multiplication, and division. However, some managerial roles involve advanced statistical modelling of employee and company performance. A link to the job description would help us tell you more.—Best Dog Ever (talk) 10:32, 16 March 2014 (UTC)

Sieve script SMS notification

My sieve filters send me SMS messages in certain circumstances that I have configured, such as when John or Jane email me as they are important contacts. I would like my sieve script to choose an apparent sender depending on whether John or Jane emails me; i.e. when John emails me the SMS forward appears to originate from his number, likewise with Jane. Is this possible? Thanks.--Leon (talk) 15:28, 16 March 2014 (UTC)

Has my WiFi network been compromised?

I happened to be in Windows File Explorer and noticed an unknown device on my network. It was listed as phone named "tmous". I right-clicked on properties and it said that it was an HTC One. I don't own an HTC One. I'm not sure what to make of this. I haven't given out my WiFi password to anyone and I live alone. The device was listed briefly in Windows File Explorer and disappeared. It had a Mac address but not an IP address. All my PCs are running Windows 8.1 except for one running XP which I am retiring. I have a Linksys WiFi Router (model #AC 900). Should I be concerned? A Quest For Knowledge (talk) 16:50, 16 March 2014 (UTC)

Yes, I suggest you change your wifi password and see if that makes it disappear. It's good to change your password regularly.--Shantavira|^{feed me} 17:13, 16 March 2014 (UTC)

Now there’s a Droid Razr. Again, there’s no IP address. Are these people trying to log into my network without knowing my password? Would a phone temporarily show up in Windows File Explorer while the phone is trying to log in to my network? A Quest For Knowledge (talk) 17:17, 16 March 2014 (UTC)

Now a third phone, this time a ZTE N800. It’s another Android phone and no IP address. I'm wondering if there's some Android app that automatically scans for wireless networks and tries to log in to them. A Quest For Knowledge (talk) 18:45, 16 March 2014 (UTC)

So, I ended up turning on Mac filtering to create a whitelist of devices I'm allowing to connect to my network. A Quest For Knowledge (talk) 12:19, 18 March 2014 (UTC)

I turned on Mac filtering and I'm still seeing phantom phones on my network. A Quest For Knowledge (talk) 22:13, 18 March 2014 (UTC)

The fact you see these devices in Windows Explorer does not mean they are connecting through WiFi. My guess you are seeing devices your PC is trying to connect to... I'll bet you have BlueTooth enabled; thats why you see no IP. — Edokter (talk) — 15:09, 19 March 2014 (UTC)

How do I disable BlueTooth? I recently upgraded my main PC to have a Bluetooth NIC however, I was not able to find an open USB connection to enable it. The NIC I bought is this.[1] A Quest For Knowledge (talk) 21:56, 19 March 2014 (UTC)

Chrome keeps on reporting

I have Chrome Version 33.0.1750.154 m, Windows 7. It keeps on reporting "VideoDowloader" was automatically removed. I have no option to disable it. Tito☸Dutta 17:59, 16 March 2014 (UTC)

Commodore 64 resolution

Look at this YouTube video, which shows clips from various Commodore 64 games. I noticed that in many of them, the resolution of the graphics seems to be higher than what the Commodore 64 is actually capable of (640×400 compared to the Commodore 64's 320×200). Why is this? Were these clips recorded on an emulator with in-built automatic smoothing of graphics or something? JIP | Talk 18:35, 16 March 2014 (UTC)

Most emulators render into an OpenGL surface of the emulated machine's native resolution and then OpenGL upscales that (with a simple bilinear interpolative scaler) when putting that onto the screen - that gives a somewhat smoother appearance. Some emulators deliberately try to emulate the characteristics (deficiencies) of the CRT displays that were used for machines like the C=64, such as adding the appearance of scanlines and chroma noise (I think Vice does that). A few emulators (like MAME) can do a proper pixel-art scale; it's a good deal easier for MAME than for a C=64 emulator like Vice, as MAME knows exactly which game it's running, and so can choose which scaling algorithm is most suited to that game's graphics, whereas a general computer emulator like one for the C=64 doesn't. -- Finlay McWalterჷTalk 18:55, 16 March 2014 (UTC)

Here's a specific example, from the source code of C=64 emulator Vice - in the Unix/Gtk variant the "screen" texture is pushed to the actual GL screen in the function exposure_callback_canvas() in source file src/arch/unix/x11/gnome/x11ui.c first calls glTexParameter() and sets the upscale and downscale functions (which are called when the output window is larger or smaller respectively than the emulated screen texture) to GL_LINEAR which "Returns the weighted average of the four texture elements that are closest to the center of the pixel being textured." -- Finlay McWalterჷTalk 20:06, 17 March 2014 (UTC)

Which games specifically? I see nothing that appears to be higher than 320x200. I don't think any fancy upscaling is being used either. You can count the pixels when there are dithering patterns or jagged diagonal lines. -- BenRG (talk) 21:05, 16 March 2014 (UTC)

For example, the very first game, Commando, exhibits this. I took a screenshot of the video and compared it to a pixel-to-pixel accurate screenshot from the actual game. The difference is evident, for example, in the status line right below the playing area. In the original game, the whole line is strictly black and white with no intermediate colours. The video, however, shows heavy anti-aliasing using several shades of gray, making it look like the resolution has doubled both horizontally and vertically. JIP | Talk 15:10, 17 March 2014 (UTC)

There are 40 characters in the status line and each one is 8x8 black and white pixels (you can see this in the grenade image, which has a checkerboard pattern). The grey pixels in the video are a side effect of several stacked image rescaling operations: probably first to 640 by pixel doubling (nearest neighbor), then to the video resolution (~468 pixels across if you're watching the 360p version, or ~625 pixels at 480p), then to the size of the video player. Compare this video of a 160x96 Intellivision game where the pixels are obviously huge rectangles. If you watch it at 480p, there are sharp lines between the pixels because 160 divides 640 and 96 divides 480. If you watch it at 360p those boundaries are "smoothed" as a side effect of the rescaling. The diagonal lines in the dungeon look smoothest at 144p, but only because they're blurrier. -- BenRG (talk) 19:29, 17 March 2014 (UTC)

Downloading a virus to study

Is it possible for the average person to download a virus in order to study it? I'd imagine that companies like Symantec and such keep them on file. Dismas|^(talk) 20:40, 16 March 2014 (UTC)

http://zeltser.com/combating-malicious-software/malware-sample-sources.html is a good start. OsmanRF34 (talk) 23:13, 16 March 2014 (UTC)

You can try https://www.grc.com/malware.htm. Out of curiosity, how do you plan to examine it? Use a VM? Or just be careful not to execute it? A Quest For Knowledge (talk) 14:50, 17 March 2014 (UTC)

Do you really mean a virus or some other kind of malware? Some are fairly benign (e.g. the Joshi virus just requires the user to type "happy birthday joshi" once a year or it hangs the system) while others may go so far as to remove essential components of your operating system or allow remote access to your desktop. For the "average person" and "not your average person" alike it seems like doing any of this on any computer that has any personal data is a bad idea. Maybe you have an old computer you can just install an operating system on and keep the OS discs handy to reformat when you're done? Don't let it connect through a router you'll use for other connections, though. --— Rhododendrites ^talk |  20:13, 17 March 2014 (UTC)

A Quest For Knowledge, it was simply a quest for knowledge. :) I don't have any plans to open one and take a look since any of them would be way above my programming knowledge. I was just curious if there were repositories of them or something where one could go get one without having to go into the more seedy spots on the Internet and pick up some unintended virus/malware while looking for one to study. And yeah, Rhododendrites, I was using virus in a more general sense which included any malicious code. Dismas|^(talk) 23:46, 17 March 2014 (UTC)

I thought I'd share an anecdotal story here. One of the first ever PC viruses in the 1990's was called Friday 13th and a computer science student managed to reverse engineer and create some source code out of it. He then changed it a bit, called it Saturday 14th, and with a group of friends tested it in the computer lab, making sure that nobody else was using the lab at the time. Well, there must have been someone logged in at that time, because Saturday 14th went 'viral' and spread around the world in no time. It does not matter what is said of this virus - I'm pretty sure it came from that guy and his friends. Moral of the story: be careful. Sandman1142 (talk) 14:12, 19 March 2014 (UTC)