Running Elasticsearch 1.4.2 or earlier? There's targeted malware going for your boxen

Yes it's years out of date but there's no such thing as security through obscurity

Cisco's security limb has spotted nefarious people targeting Elasticsearch clusters using relatively ancient vulns to plant malware, cryptocurrency miners and worse – though it does root out some other cybercrims’ dodgy wares, cuckoo-style.…

from The Register