Question about DNS queries

[steve2470]

Hello all. I have OpenDNS.com, which enables me to regulate my son's internet surfing during study hours. On the opendns page for "all queries", some of the URL's I know he did and they are OK, some I did, and then the rest I'm not sure about.

I go to a lot of pages (here at DU for example) that contain links for Youtube, Facebook and Twitter. Here's my question: When you surf to a page with links, do all of the page's links do a DNS query or only some of them ? Thanks for your time.

Steve

[discntnt_irny_srcsm]

1. As far as I know...

...all web addresses not given by IP address are resolved to one either by 'hosts' file on the pc, a device on your LAN or by whatever names server you specify.

[steve2470]

2. for example, the Facebook entries on the dns queries page

I can see my son going to Facebook one time to see if he can do it, and discovering it's blocked. According to the stats right now, Facebook.com has been requested 25 times and blocked each time.

I see a lot of entries that I'm sure he didn't request and I know I didn't request, and my only other explanation is the links on the pages I accessed requested those DNS lookups.

[discntnt_irny_srcsm]

3. Some pages on a commercial site...

...will have an ad, banner or content that is sourced at another site. This may explain what you are seeing.

[limpyhobbler]

4. yeah alot of things on a web page will lead to extra dns queries.

Any images on a page will generate a DNS lookup. The images aren't necessarily on the same server as the webpage so you might see a separate DNS request resolve the name for that site. That includes advertising content.

Same for any video or audio embedded content or flash applications, java applets, etc.

[HopeHoops]

5. Generally, the query only happens when you click a link - HOWEVER...

As DU users often use Photobucket or another off-site image storage location, pages with an image link will do the DNS search in order to load the picture. The same is true with advertisements, and scripts can do their own queries. As for the ones in the link (like OpenDNS.com in your OP), by opening this page I am NOT causing a DNS query. If I click on your link, it will. The router should have a logging feature you can turn on. I generally leave it off unless I'm trouble-shooting because it slows everything down.

As for your son, if you're worried about porn, give it up. It's everywhere. All you have to do is turn off history and JavaScript while browsing and clear the recent files list when you're done and the computer looks just fine afterward. If you're using the router to monitor the activity, accept the reality unless you hit something like HairyPregnantHorseFuckers.com. That might indicate a problem. And yes, I made that one up. No clue if it exists or not and I'm not going to check.

I've had similar problems with my three daughters, but it is mostly games or social networking that's the problem. Restricting time, just shutting off the wireless entirely, and making them do their homework in an open area have all been marginally effective. It's their world now. I watched WAY too much bullshit like Gilligan's Island when I was a kid. That was my world. If the grades suffer, that's a major reason to get tough. If the grades are fine, just chill.

[ChromeFoundry]

6. Many items on a web page will perform a DNS Query

Not only image src attributes and ad content, but references to stylesheets, javascript, iFrames, javascript prefetching, etc...

If you really want to know where the kiddies are going and what page caused the request... you'd need to set up a transparent proxy server and look at the log files. Your router would need to block port 80 and 443 from all internal IP addresses except for your proxy server. If you enable proxy caching, you might even get a slight performance increase.

Not sure if it's practical in your environment, but I can tell you from experience, the open source and free packages currently available for Linux, Windows and FreeBSD are nothing short of amazing and very easy to setup in less than an hour (if you have a spare workstation and know how to configure your router).

[Go Vols]

7. or

install a keylogger if you are ...