This has happened again, to the same node. The 4 hits came between approx. 16:39:57 and 16:40:27 EST on July 8. 4 offending IPs, one hit each: 1.50.251.122, 210.72.140.17, 119.4.5.55, 115.200.236.120 (they are all from China, per Apnic). They hit against the same hex-string rule as before.