I see an IDS alert for ET POLICY DropBox User Content Access over SSL ( Emerging Threats Pro rules)
And it seems this is a source of malware: http://www.scumware.org/report/dl.dropboxusercontent.com.html
Stumbled upon this via these scan results: http://urlquery.net/report.php?id=1431028186968
I get an error 404 for http://dl.dropboxusercontent.com/
Netcraft Risk Status 5 red out of 10: http://dl.dropboxusercontent.com/ (see the IP migration patterns!)
Resolve Domain Name
WARNING: Could not resolve domain dropboxusercontent.com…
Registered and no website: http://whois.domaintools.com/dropboxusercontent.com
See dmarc info: https://dmarcian.com/dmarc-inspector/dropboxusercontent.com
= v=DMARC1; p=none; fo=1; rua=mailto:dropbox@-rua.agari.com; ruf=mailto:dropbox@-ruf.agari.com
dl.dropboxusercontent.com,Ghosted,ZeuS :o cleansed at a certain date: https://zeustracker.abuse.ch/monitor.php?host=dl.dropboxusercontent.com - but it still could be active as a bitcoin miner:
https://bitcointalk.org/index.php?topic=1011611.5;wap2
polonus