<s>
A	O
global	O
wave	O
of	O
cyberattacks	O
and	O
data	O
breaches	O
began	O
in	O
January	O
2021	O
after	O
four	O
zero-day	O
exploits	O
were	O
discovered	O
in	O
on-premises	B-General_Concept
Microsoft	B-Operating_System
Exchange	I-Operating_System
Servers	I-Operating_System
,	O
giving	O
attackers	O
full	O
access	O
to	O
user	O
emails	O
and	O
passwords	O
on	O
affected	O
servers	O
,	O
administrator	B-Application
privileges	I-Application
on	O
the	O
server	O
,	O
and	O
access	O
to	O
connected	O
devices	O
on	O
the	O
same	O
network	O
.	O
</s>
<s>
On	O
2	O
March	O
2021	O
,	O
Microsoft	O
released	O
updates	O
for	O
Microsoft	B-Protocol
Exchange	I-Protocol
Server	I-Protocol
2010	I-Protocol
,	I-Protocol
2013	I-Protocol
,	I-Protocol
2016	I-Protocol
and	I-Protocol
2019	I-Protocol
to	O
patch	O
the	O
exploit	O
;	O
this	O
does	O
not	O
retroactively	O
undo	O
damage	O
or	O
remove	O
any	O
backdoors	O
installed	O
by	O
attackers	O
.	O
</s>
<s>
On	O
22	O
March	O
2021	O
,	O
Microsoft	O
announced	O
that	O
in	O
92%	O
of	O
Exchange	B-Operating_System
servers	I-Operating_System
the	O
exploit	O
has	O
been	O
either	O
patched	O
or	O
mitigated	O
.	O
</s>
<s>
The	O
first	O
breach	O
of	O
a	O
Microsoft	B-Operating_System
Exchange	I-Operating_System
Server	I-Operating_System
instance	O
was	O
observed	O
by	O
cybersecurity	O
company	O
Volexity	O
on	O
6	O
January	O
2021	O
.	O
</s>
<s>
On	O
10	O
March	O
2021	O
,	O
security	O
researcher	O
Nguyen	O
Jang	O
posted	O
proof-of-concept	O
code	O
to	O
Microsoft-owned	O
GitHub	B-Application
on	O
how	O
the	O
exploit	O
works	O
,	O
totaling	O
169	O
lines	O
of	O
code	O
;	O
the	O
program	O
was	O
intentionally	O
written	O
with	O
errors	O
so	O
that	O
while	O
security	O
researchers	O
could	O
understand	O
how	O
the	O
exploit	O
works	O
,	O
malicious	O
actors	O
would	O
not	O
be	O
able	O
to	O
use	O
the	O
code	O
to	O
access	O
servers	O
.	O
</s>
<s>
Later	O
that	O
day	O
,	O
GitHub	B-Application
removed	O
the	O
code	O
as	O
it	O
"	O
contains	O
proof	O
of	O
concept	O
code	O
for	O
a	O
recently	O
disclosed	O
vulnerability	O
that	O
is	O
being	O
actively	O
exploited	O
"	O
.	O
</s>
<s>
The	O
attacks	O
came	O
shortly	O
after	O
the	O
2020	O
United	O
States	O
federal	O
government	O
data	O
breach	O
,	O
which	O
also	O
saw	O
the	O
compromising	O
of	O
Microsoft	O
's	O
Outlook	B-Protocol
web	I-Protocol
app	I-Protocol
and	O
supply	O
chain	O
.	O
</s>
<s>
Hafnium	O
is	O
known	O
to	O
install	O
the	O
web	B-Protocol
shell	I-Protocol
China	B-Protocol
Chopper	I-Protocol
.	O
</s>
<s>
In	O
a	O
July	O
19	O
,	O
2021	O
joint	O
statement	O
,	O
the	O
US	O
,	O
UK	O
,	O
EU	O
,	O
NATO	O
,	O
and	O
other	O
Western	O
nations	O
accused	O
the	O
Ministry	O
of	O
State	O
Security	O
(	O
MSS	O
)	O
of	O
perpetrating	O
the	O
Exchange	O
breach	O
,	O
along	O
with	O
other	O
cyberattacks	O
,	O
"	O
attributing	O
with	O
a	O
high	O
degree	O
of	O
confidence	O
that	O
malicious	O
cyber	O
actors	O
affiliated	O
with	O
PRC	O
’s	O
MSS	O
conducted	O
cyber	O
espionage	O
operations	O
utilizing	O
the	O
zero-day	O
vulnerabilities	O
in	O
Microsoft	B-Operating_System
Exchange	I-Operating_System
Server	I-Operating_System
disclosed	O
in	O
early	O
March	O
2021.	O
"	O
</s>
<s>
Hackers	O
took	O
advantage	O
of	O
four	O
separate	O
zero-day	O
vulnerabilities	O
to	O
compromise	O
Microsoft	B-Operating_System
Exchange	I-Operating_System
servers	I-Operating_System
 '	O
Outlook	B-Protocol
Web	I-Protocol
Access	I-Protocol
(	O
OWA	O
)	O
,	O
giving	O
them	O
access	O
to	O
victims	O
 '	O
entire	O
servers	O
and	O
networks	O
as	O
well	O
as	O
to	O
emails	O
and	O
calendar	O
invitations	O
,	O
only	O
at	O
first	O
requiring	O
the	O
address	O
of	O
the	O
server	O
,	O
which	O
can	O
be	O
directly	O
targeted	O
or	O
obtained	O
by	O
mass-scanning	O
for	O
vulnerable	O
servers	O
;	O
the	O
attacker	O
then	O
uses	O
two	O
exploits	O
,	O
the	O
first	O
allowing	O
an	O
attacker	O
to	O
connect	O
to	O
the	O
server	O
and	O
falsely	O
authenticate	O
as	O
a	O
standard	O
user	O
.	O
</s>
<s>
With	O
that	O
,	O
a	O
second	O
vulnerability	O
can	O
then	O
be	O
exploited	O
,	O
escalating	O
that	O
user	O
access	O
to	O
administrator	B-Application
privileges	I-Application
.	O
</s>
<s>
The	O
final	O
two	O
exploits	O
allow	O
attackers	O
to	O
upload	O
code	O
to	O
the	O
server	O
in	O
any	O
location	O
they	O
wish	O
,	O
that	O
automatically	O
runs	O
with	O
these	O
administrator	B-Application
privileges	I-Application
.	O
</s>
<s>
Attackers	O
then	O
typically	O
use	O
this	O
to	O
install	O
a	O
web	B-Protocol
shell	I-Protocol
,	O
providing	O
a	O
backdoor	O
to	O
the	O
compromised	O
server	O
,	O
which	O
gives	O
hackers	O
continued	O
access	O
to	O
the	O
server	O
as	O
long	O
as	O
both	O
the	O
web	B-Protocol
shell	I-Protocol
remains	O
active	O
and	O
the	O
Exchange	B-Operating_System
server	I-Operating_System
remains	O
on	O
.	O
</s>
<s>
Through	O
the	O
web	B-Protocol
shell	I-Protocol
installed	O
by	O
attackers	O
,	O
commands	O
can	O
be	O
run	O
remotely	O
.	O
</s>
<s>
Among	O
the	O
actions	O
observed	O
are	O
the	O
downloading	O
of	O
all	O
emails	O
from	O
servers	O
,	O
downloading	O
the	O
passwords	O
and	O
email	O
addresses	O
of	O
users	O
as	O
Microsoft	O
Exchange	O
stores	O
these	O
unencrypted	O
in	O
memory	B-General_Concept
,	O
adding	O
users	O
,	O
adding	O
further	O
backdoors	O
to	O
affected	O
systems	O
,	O
accessing	O
other	O
systems	O
in	O
the	O
network	O
that	O
are	O
unsusceptible	O
to	O
the	O
original	O
exploit	O
,	O
and	O
installing	O
ransomware	O
.	O
</s>
<s>
As	O
patching	O
the	O
Exchange	B-Operating_System
server	I-Operating_System
against	O
the	O
exploit	O
does	O
not	O
retroactively	O
remove	O
installed	O
backdoors	O
,	O
attackers	O
continue	O
to	O
have	O
access	O
to	O
the	O
server	O
until	O
the	O
web	B-Protocol
shell	I-Protocol
,	O
other	O
backdoors	O
and	O
user	O
accounts	O
added	O
by	O
attackers	O
are	O
removed	O
.	O
</s>
<s>
On	O
27	O
and	O
28	O
February	O
2021	O
,	O
there	O
was	O
an	O
automated	O
attack	O
,	O
and	O
on	O
2	O
and	O
3	O
March	O
2021	O
,	O
attackers	O
used	O
a	O
script	O
to	O
return	O
to	O
the	O
addresses	O
to	O
drop	O
a	O
web	B-Protocol
shell	I-Protocol
to	O
enable	O
them	O
to	O
return	O
later	O
.	O
</s>
<s>
Microsoft	B-Operating_System
Exchange	I-Operating_System
Server	I-Operating_System
versions	O
of	O
2010	O
,	O
2013	O
,	O
2016	O
and	O
2019	O
were	O
confirmed	O
to	O
be	O
susceptible	O
,	O
although	O
vulnerable	O
editions	O
are	O
yet	O
to	O
be	O
fully	O
determined	O
.	O
</s>
<s>
Cloud-based	O
services	O
Exchange	O
Online	O
and	O
Office	B-Operating_System
365	I-Operating_System
are	O
not	O
affected	O
.	O
</s>
<s>
The	O
attack	O
was	O
discovered	O
after	O
attackers	O
were	O
discovered	O
downloading	O
all	O
emails	O
belonging	O
to	O
specific	O
users	O
on	O
separate	O
corporate	O
Exchange	B-Operating_System
servers	I-Operating_System
.	O
</s>
<s>
One	O
APT	O
group	O
was	O
identified	O
deploying	O
PowerShell	B-Application
downloaders	O
,	O
using	O
affected	O
servers	O
for	O
cryptocurrency	O
mining	O
.	O
</s>
<s>
Advanced	O
Intel	O
detected	O
one	O
of	O
Acer	O
's	O
Microsoft	B-Operating_System
Exchange	I-Operating_System
servers	I-Operating_System
first	O
being	O
targeted	O
on	O
5	O
March	O
2021	O
.	O
</s>
<s>
On	O
2	O
March	O
2021	O
,	O
the	O
Microsoft	O
Security	O
Response	O
Center	O
(	O
MSRC	O
)	O
publicly	O
posted	O
an	O
out-of-band	O
Common	O
Vulnerabilities	O
and	O
Exposures	O
(	O
CVE	O
)	O
release	O
,	O
urging	O
its	O
clients	O
to	O
patch	O
their	O
Exchange	B-Operating_System
servers	I-Operating_System
to	O
address	O
a	O
number	O
of	O
critical	O
vulnerabilities	O
.	O
</s>
<s>
On	O
15	O
March	O
,	O
Microsoft	O
released	O
a	O
one-click	O
PowerShell	B-Application
tool	O
,	O
The	O
Exchange	O
On-Premises	B-General_Concept
Mitigation	O
Tool	O
,	O
which	O
installs	O
the	O
specific	O
updates	O
protecting	O
against	O
the	O
threat	O
,	O
runs	O
a	O
malware	B-Application
scan	I-Application
which	O
also	O
detects	O
installed	O
web	B-Protocol
shells	I-Protocol
,	O
and	O
removes	O
threats	O
that	O
were	O
detected	O
;	O
this	O
is	O
recommended	O
as	O
a	O
temporary	O
mitigation	O
measure	O
,	O
as	O
it	O
does	O
not	O
install	O
other	O
available	O
updates	O
.	O
</s>
<s>
Other	O
official	O
bodies	O
expressing	O
concerns	O
included	O
the	O
White	B-Application
House	I-Application
,	O
Norway	O
's	O
National	O
Security	O
Authority	O
and	O
the	O
Czech	O
Republic	O
's	O
Office	O
for	O
Cyber	O
and	O
Information	O
Security	O
.	O
</s>
<s>
On	O
7	O
March	O
2021	O
,	O
CNN	B-Architecture
reported	O
that	O
the	O
Biden	O
administration	O
was	O
expected	O
to	O
form	O
a	O
task	O
force	O
to	O
address	O
the	O
breach	O
;	O
the	O
Biden	O
administration	O
has	O
invited	O
private-sector	O
organizations	O
to	O
participate	O
in	O
the	O
task	O
force	O
and	O
will	O
provide	O
them	O
with	O
classified	O
information	O
as	O
deemed	O
necessary	O
.	O
</s>
<s>
According	O
to	O
White	B-Application
House	I-Application
press	O
secretary	O
Jen	O
Psaki	O
,	O
the	O
administration	O
is	O
not	O
ruling	O
out	O
future	O
consequences	O
for	O
China	O
.	O
</s>
