Would it be very had to sniff traffic and brute force the secret otherwise?
In any case, this is after all just the free stuff. If you believe that what they are offering is the real deal, of course, and with this release I'd put the probability at >0.
Or maybe there are lots of overseas networks where they enable SNMP and leave the community string "public"?
(Also: how batshit crazy is it that the ASA will let you use "public" as your community string, let alone default to it?)
No! For example, at one place I was employed at, the switches had different VLANs - one for private internal network, one which had external (direct) internet access, one for VoIP telephones, one for printers, one for servers and one for BYOD external consultants. Basically, compartmentalization - and everything was firewalled, and every cross-VLAN access had to be separately allowed.
So this exploit (or, for that matter any switch/router exploit) can be used not just for persisting, but for escalating privileges. Assume you have hacked a fax printer via the telephone line (hey, given that, I'm tempted to actually grab a modem and do some fuzzing with my fax printer...), you can then use its network connection to punch holes in the firewall and spread.
Whereas persisting onto an ASA sounds like an actually widely useful capability! The ASAs don't get reimaged during incident response.
Indeed, yes, but entities large enough to afford dedicated teams to run hundreds of pieces of Cisco gear with proper segmentation etc. usually also tend to be those of most interest to any espionage outfit.
Last I heard, ex-employer switched from huge VLAN switches to dedicated, unconnected switches for each network part after Snowden. Given the leak here, I'd say their fear wasn't totally unjustified.
In environments I've seen, the network management network is the thing most likely to be isolated first.
Again the case I'm making is that this particular bug is really only useful for persisting onto networks you've already compromised.
I'm thinking specifically of my old company, which used Nagios to monitor a few hundred VMs on AWS in addition to the several thousand servers & all the networking gear running locally.