title: Unknown beacon calls to ad servers
body: <p>On my site I found that there are lots of beacon calls happening like this</p>
  
  <p><div class="snippet" data-lang="js" data-hide="true">
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;img src="http://ib.adnxs.com/getuid?http://cmap.an.ace.advertising.com/cfcm.ashx?providerId=1006&amp;amp;appnexus_uid=$UID" width="1" height="1" class=""&gt;
  &lt;img src="http://tags.bluekai.com/site/4470?id=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://dpm.demdex.net/ibs:dpid=416&amp;amp;dpuuid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://s.thebrighttag.com/cs?tp=ao&amp;amp;aolid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://d.turn.com/r/du/id/L2NzaWQvMS9tcGlkLzMwNTU3ODEz/mpuid/TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://d.p-td.com/r/dt/id/L21rdC80L21waWQvMzMxNTMzNg/mpuid/TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://e.nexac.com/e/aol_sync.xgi?na_exid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://idsync.rlcdn.com/362408.gif?partner_uid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://adadvisor.net/adscores/g.pixel?sid=9201883608&amp;amp;aid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://p.acxiom-online.com/pixel/smt?pid=3034&amp;amp;t=3034&amp;amp;ot=pixel&amp;amp;uid=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://ckm-m.xp1.ru4.com/cx?_i=42102464&amp;amp;_u=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;
  &lt;img src="http://d.agkn.com/pixel/2134/?dpids=131902&amp;amp;plaid=1&amp;amp;camid=03222013&amp;amp;partner_id=TA3672b770-d9d0-11e4-b9de-00163e82216c" width="1" height="1" class=""&gt;</code></pre>
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  <p>After digging it further I found this call an 1x1 pixel iframe with src <code>http://cmap.uac.ace.advertising.com/um.ashx?site=852146&amp;rCode=1&amp;cb=4893281</code> on the page. This iframe is adding all these beacon calls to different ad servers. My question is - </p>
  
  <ol>
  <li>What purpose do these beacons serve ?</li>
  <li>Can they cause harm to users of my site ?</li>
  </ol>