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I am able to ping certain domains (like google.com, imgur.com), while most others I tried have 100% packet loss. For example, I can't ping dit.rs, b92.net, novosti.rs, they all have 100% packet loss. Additionally, I know I used to be able to ping those urls before (a couple of months back). Also, if I try to ping rts.rs I get:

From dist-bg-2-te5-4.eunet.rs (194.247.195.138) icmp_seq=2 Packet filtered

I don't know what this means. I'm freaking out because I'm afraid it might be a trojan or some other malware. Any help?

Rinzwind
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  • eunet.rs looks like an ISP. Is it your ISP? – muru Dec 23 '14 at 15:22
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    Fwiw I can't ping those domains either. Perhaps those domains have been set up to block pings? – ike Dec 23 '14 at 15:43
  • @muru eunet.rs is both ISP and hosting provider. It's not my ISP, it appears to be hosting the rts.rs site. – Томица Кораћ Dec 23 '14 at 15:45
  • @ike I'm pretty sure I was able to ping at least some of them before. Also, I even own some of these domains (dit.rs), and am not aware how it could be configured to block pings? Additionally, I can only ping very few domains, out of some 50 or so that I tested, I only got responses for a few (like google.com or facebook.com). Even ping twitter.com returns 100% packet loss... – Томица Кораћ Dec 23 '14 at 15:49
  • @ТомицаКораћ you could own the domain, but the hosting provider may filter out unwanted traffic (allowing only SSH and HTTP, for example) as a security measure. Check your provider's control panel. – muru Dec 23 '14 at 15:57
  • That could just mean the settings were changed. OTOH ping twitter.com works for me. – ike Dec 23 '14 at 16:01
  • @ike I'm not able to ping them either, so this looks like an upstream issue (hosts blocking ping requests) rather than a local machine issue. If those sites are resolving and loading, it's not a problem. – douggro Dec 23 '14 at 16:05
  • Thank you all for commenting. I'm going to ask my registrar about the domain I own. As for the rest, I guess it sounds logical what you said, since I'm able to load the sites, then probably pinging their urls isn't allowed. – Томица Кораћ Dec 23 '14 at 16:45

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As suggested by @muru and @ike, the reason why I wasn't getting response from pinging my urls was because my hosting company blocks pings. Here is their answer:

Unfortunately, ping is not supported on our server. As you may be aware, Web servers come under attack by unscrupulous hackers from time to time. One of the attacks that hackers sometimes use is a Denial of Service attack, which is accomplished by sending millions of pings (routine system status requests) to a server over a short amount of time. This cripples the receiving machine, which spends all of its time responding to pings rather than doing its job like serving customer web pages.

To defend against these attacks, our server not return pings. The reports you are receiving from ping command do not reflect the availability of your Web site. Our server uptime levels have exceeded 99.999% over the past several months. In fact, it is in part because of our policy not to return pings that your Web site is performing as well as it is.

Many ISPs are resorting to this kind of strategy in order to maintain the level of service expected by their legitimate users.

I can only guess that the same reason is good for other pings not coming back.

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