SOURCE

<div class='border'></div>

div{
  width:30em;
  height:20em;
  display:inline-block;
  
}
@keyframes ants{ to {background-position:100%}}
.border{
  padding:1em;
  border:1em solid transparent;
  background:linear-gradient(white, white) padding-box,
	            repeating-linear-gradient(-45deg, red 0, red 12.5%, transparent 0, transparent 25%, 
	              #58a 0, #58a 37.5%, transparent 0, transparent 50%) 0 / 6em 6em;
  animation:ants 12s linear infinite;
}