Hi,
We got hit with a crytolocker/bitlocker attack last week. Fortunately we
have good backups so were able to restore, although 3gb of data took
some time to do.
What I want to do is go over what happened and see what approaches other
people have for these threats.
First thing we noticed was on Friday morning when somebody pointed out
that their files had been mashed. Here's a few examples of what the
files got changed to:
/data/admin/misc files/FACTORY INFORMATION/fnwih0ocf.hoo7
/data/admin/misc files/FACTORY INFORMATION/g99q1kfz5.p9k0
/data/admin/misc files/FACTORY INFORMATION/og0u9pb.0gd
/data/admin/misc files/FACTORY INFORMATION/tb4qz.775x0
/data/admin/misc files/FACTORY INFORMATION/znxis7hgu.k7h
/data/admin/misc files/fi19fgq2r.69t
/data/admin/misc files/fjs6r76n.8gup
/data/admin/misc files/h2c0ew6pr.1gpd
/data/admin/misc files/h8jgb.c4v9
/data/admin/misc files/Halls Fashion/535p0e.ugc5a
/data/admin/misc files/Halls Fashion/halorr3vet.s9
/data/admin/misc files/Halls Fashion/nbhqgk5.a8ihp
/data/admin/misc files/hs93hlb9.9p
/data/admin/misc files/hxplu62l.mc9
/data/admin/misc files/i4jden.y7kx7
/data/admin/misc files/jaiytu55s.w2
/data/admin/misc files/kmp49j76.4b
Looking at the logs we soon found which machine it was although that
person had gone home on the Thursday and was not due back until the Tuesday.
Restored data and when the user got back we booted the machine up (not
connected to network!) and have since done scan using AVG,
Superantispyware, Avira, spybot search and destroy, kaspersky and
malware bytes and still found nothing. We don't know if the virus was
just memory resident or how it worked but obviously want to find out.
Scanned all his emails and nothing (his files stored in IMAP folders).
Nothing obvious in internet logs. Checked all processes running,
startup programs, network setup etc etc. We'll probably just wipe the
machine and start again but would be nice to know what happened.
Lately we have been getting more and more phishing emails from random
users (pretending to be say DHL or some other company) with say an
attachment invoicexxx.doc or perhaps .docx .xls etc (where xxx is a
random number) which will turn out to be infected but not at the time
the email was received. I.e the virus is too new to be detected. We
have run lots of these through our own virus scanner (AVG) and say
https://www.virustotal.com/
and they have come up with nothing until hours later (which could be too
late). Some show infected a couple of hours later and some maybe next day.
This latest development is very difficult to defend against if you
cannot scan the file and confirm it is infected. Our mail server as AV
software which scans files but didn't pick these up and even if users
are really conscientious and scan before opening it does not show up as
infected.
We have now started implementing a white list of people who can send in
invoicexxx.doc files. Anyone not on the list then the attachment is
removed and put a message in to inform the user.
We are now reviewing procedures to defend against a machine with admin
rights being infected.
What is important is to be able to detect ASAP when files are starting
to get renamed. I have just developed a standalone APP that will scan
network drives and look at file names. I got a list of known extensions
off the internet and put them in a table. The app compares the file
extension with the list and emails you anything different. If these
files are safe you can load them into an exclusion table. If you run
this regularly it should pick up these names very quickly.
What other security approaches are you using?
TIA
--
Peter Cushing
IT Department
WHISPERING SMITH
Brave Soul at Pure London
14th-16th Feb
Stand F44
Mens and Womens
SS16 Stock and AW16 Preview
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