<s>
Valve	B-Application
Anti-Cheat	I-Application
(	O
VAC	O
)	O
is	O
an	O
anti-cheat	O
software	O
product	O
developed	O
by	O
Valve	O
as	O
a	O
component	O
of	O
the	O
Steam	B-Application
platform	O
,	O
first	O
released	O
with	O
Counter-Strike	B-Application
in	O
2002	O
.	O
</s>
<s>
It	O
may	O
kick	O
players	O
from	O
the	O
game	O
if	O
it	O
detects	O
errors	O
in	O
their	O
system	O
's	O
memory	B-Architecture
or	O
hardware	O
.	O
</s>
<s>
After	O
the	O
player	O
is	O
notified	O
,	O
access	O
to	O
online	O
"	O
VAC	O
protected	O
"	O
servers	O
of	O
the	O
game	O
the	O
player	O
cheated	O
in	O
is	O
permanently	O
revoked	O
and	O
additional	O
restrictions	O
are	O
applied	O
to	O
the	O
player	O
's	O
Steam	B-Application
account	O
.	O
</s>
<s>
In	O
2001	O
,	O
Even	B-Application
Balance	I-Application
Inc.	O
,	O
the	O
developers	O
of	O
the	O
anti-cheat	O
software	O
PunkBuster	B-Application
designed	O
for	O
Counter-Strike	B-Application
and	O
Half-Life	O
mods	O
,	O
stopped	O
supporting	O
the	O
games	O
as	O
they	O
had	O
no	O
support	O
from	O
Valve	O
.	O
</s>
<s>
VAC	O
's	O
initial	O
release	O
was	O
with	O
Counter-Strike	B-Application
in	O
2002	O
.	O
</s>
<s>
The	O
duration	O
of	O
the	O
ban	O
was	O
increased	O
over	O
time	O
;	O
players	O
were	O
banned	O
for	O
1	O
year	O
and	O
5	O
years	O
,	O
until	O
VAC2	B-Application
was	O
released	O
in	O
2005	O
,	O
when	O
any	O
new	O
bans	O
became	O
permanent	O
.	O
</s>
<s>
VAC2	B-Application
was	O
announced	O
in	O
February	O
2005	O
and	O
began	O
beta	O
testing	O
the	O
following	O
month	O
.	O
</s>
<s>
It	O
can	O
detect	O
versions	O
of	O
"	O
OGC	O
's	O
OpenGl	B-Application
Hack	O
"	O
,	O
can	O
detect	O
OpenGL	B-Application
cheats	O
,	O
and	O
also	O
detects	O
CD	B-Application
key	I-Application
changers	O
as	O
cheats	O
.	O
</s>
<s>
RAM/hardware	O
errors	O
detected	O
by	O
VAC	O
may	O
kick	O
the	O
player	O
from	O
the	O
server	O
,	O
but	O
not	O
ban	O
them	O
.	O
</s>
<s>
In	O
February	O
2010	O
,	O
the	O
VAC	O
Team	O
consisted	O
of	O
Steam	B-Application
's	O
lead	O
engineer	O
John	O
Cook	O
and	O
his	O
team	O
of	O
16	O
engineers	O
.	O
</s>
<s>
In	O
July	O
2010	O
,	O
several	O
players	O
who	O
successfully	O
used	O
information	O
leaked	O
from	O
Valve	O
to	O
increase	O
their	O
chances	O
of	O
finding	O
a	O
rare	O
Team	B-Application
Fortress	I-Application
2	I-Application
weapon	O
called	O
the	O
Golden	O
Wrench	O
were	O
banned	O
by	O
VAC	O
.	O
</s>
<s>
During	O
the	O
same	O
month	O
,	O
approximately	O
12,000	O
owners	O
of	O
Call	B-Application
of	I-Application
Duty	I-Application
:	I-Application
Modern	I-Application
Warfare	I-Application
2	I-Application
were	O
banned	O
when	O
Steam	B-Application
updated	O
a	O
DLL	O
file	O
on	O
disk	O
after	O
it	O
had	O
been	O
loaded	O
into	O
memory	B-Architecture
by	O
the	O
game	O
,	O
causing	O
a	O
false	O
positive	O
detection	O
.	O
</s>
<s>
These	O
bans	O
were	O
revoked	O
and	O
those	O
affected	O
received	O
a	O
free	O
copy	O
of	O
Left	B-Application
4	I-Application
Dead	I-Application
2	I-Application
or	O
an	O
extra	O
copy	O
to	O
send	O
as	O
a	O
gift	O
.	O
</s>
<s>
In	O
February	O
2014	O
,	O
rumors	O
spread	O
that	O
the	O
system	O
was	O
monitoring	O
websites	O
users	O
had	O
visited	O
by	O
accessing	O
their	O
DNS	B-Protocol
cache	I-Protocol
.	O
</s>
<s>
Gabe	O
Newell	O
responded	O
via	O
Reddit	B-Application
,	O
clarifying	O
that	O
the	O
purpose	O
of	O
the	O
check	O
was	O
to	O
act	O
as	O
a	O
secondary	O
counter-measure	O
to	O
detect	O
kernel	B-Operating_System
level	I-Operating_System
cheats	I-Operating_System
,	O
and	O
that	O
it	O
affected	O
fewer	O
than	O
0.1	O
%	O
of	O
clients	O
checked	O
which	O
resulted	O
in	O
570	O
bans	O
.	O
</s>
<s>
The	O
system	O
has	O
been	O
criticized	O
for	O
failing	O
to	O
detect	O
LMAOBOX	O
,	O
a	O
popular	O
cheat	O
program	O
for	O
Team	B-Application
Fortress	I-Application
2	I-Application
,	O
until	O
May	O
2016	O
,	O
which	O
resulted	O
in	O
a	O
wave	O
of	O
bans	O
.	O
</s>
<s>
In	O
February	O
2017	O
,	O
Valve	O
announced	O
plans	O
to	O
introduce	O
a	O
machine-learning	O
approach	O
to	O
detecting	O
cheats	O
in	O
Counter-Strike	B-Application
:	I-Application
Global	I-Application
Offensive	I-Application
,	O
and	O
that	O
an	O
initial	O
version	O
of	O
the	O
system	O
was	O
already	O
in	O
place	O
,	O
which	O
would	O
automatically	O
mark	O
players	O
for	O
manual	O
detection	O
by	O
players	O
through	O
the	O
"	O
Overwatch	O
"	O
system	O
.	O
</s>
<s>
In	O
March	O
2018	O
,	O
Valve	O
publicized	O
said	O
machine-learning	O
based	O
approach	O
in	O
a	O
talk	O
at	O
the	O
Games	O
Developer	O
Conference	O
,	O
naming	O
it	O
VACNet	B-Application
.	O
</s>
<s>
It	O
uses	O
Signature	B-Algorithm
Scanning	I-Algorithm
to	O
detect	O
possible	O
cheats	O
when	O
scanning	O
the	O
computer	B-General_Concept
's	I-General_Concept
memory	I-General_Concept
and	O
processes	B-Operating_System
.	O
</s>
<s>
Whenever	O
an	O
anomaly	O
is	O
detected	O
,	O
an	O
incident	O
report	O
is	O
created	O
and	O
compared	O
to	O
a	O
database	O
of	O
banned	O
applications	B-Application
and/or	O
analyzed	O
by	O
Valve	O
engineers	O
.	O
</s>
<s>
According	O
to	O
Steam	B-Application
's	O
lead	O
engineer	O
John	O
Cook	O
,	O
to	O
stop	O
the	O
anti-cheat	O
software	O
itself	O
from	O
being	O
exploited	O
,	O
"	O
The	O
software	O
is	O
constantly	O
updated	O
and	O
sent	O
down	O
in	O
small	O
portions	O
for	O
the	O
servers	O
as	O
needed	O
,	O
so	O
hackers	O
only	O
get	O
to	O
see	O
small	O
portions	O
of	O
it	O
running	O
at	O
any	O
particular	O
time	O
.	O
</s>
<s>
Players	O
may	O
also	O
report	O
players	O
they	O
suspect	O
of	O
cheating	O
through	O
their	O
Steam	B-Application
Community	O
profile	O
,	O
although	O
players	O
are	O
not	O
banned	O
from	O
these	O
reports	O
alone	O
.	O
</s>
<s>
If	O
a	O
cheat	O
is	O
found	O
,	O
the	O
player	O
's	O
Steam	B-Application
account	O
will	O
be	O
flagged	O
as	O
cheating	O
immediately	O
,	O
but	O
the	O
player	O
will	O
not	O
receive	O
any	O
indication	O
of	O
the	O
detection	O
.	O
</s>
<s>
Valve	O
's	O
Source	B-Application
games	O
,	O
GoldSrc	B-Application
games	O
,	O
Unreal	B-Operating_System
Engine	I-Operating_System
games	O
)	O
.	O
</s>
<s>
Steam	B-Application
Family	O
Sharing	O
allows	O
users	O
to	O
share	O
their	O
video	O
game	O
library	O
with	O
another	O
Steam	B-Application
user	O
to	O
download	O
and	O
play	O
,	O
but	O
games	O
that	O
the	O
player	O
is	O
VAC	O
banned	O
from	O
cannot	O
be	O
shared	O
.	O
</s>
<s>
Banned	O
users	O
also	O
cannot	O
contribute	O
to	O
the	O
Steam	B-Application
Translation	O
Server	O
project	O
,	O
that	O
allows	O
users	O
to	O
contribute	O
new	O
translations	O
of	O
Steam	B-Application
and	O
its	O
games	O
.	O
</s>
<s>
Denotes	O
GoldSrc	B-Application
games	O
,	O
if	O
a	O
player	O
is	O
banned	O
in	O
one	O
of	O
these	O
games	O
they	O
are	O
banned	O
from	O
all	O
of	O
them	O
.	O
</s>
<s>
Denotes	O
Source	B-Application
engine	I-Application
games	O
,	O
if	O
a	O
player	O
is	O
banned	O
in	O
one	O
of	O
these	O
games	O
they	O
are	O
banned	O
from	O
all	O
of	O
them	O
.	O
</s>
<s>
The	O
user	O
's	O
Steam	B-Application
profile	O
is	O
also	O
marked	O
with	O
"	O
ban(s )	O
on	O
record	O
"	O
,	O
which	O
is	O
publicly	O
visible	O
and	O
cannot	O
be	O
hidden	O
,	O
regardless	O
of	O
the	O
profile	O
visibility	O
of	O
the	O
banned	O
account	O
.	O
</s>
<s>
VAC	B-Application
bans	I-Application
become	O
hidden	O
to	O
other	O
users	O
after	O
seven	O
years	O
of	O
not	O
getting	O
another	O
VAC	B-Application
ban	I-Application
.	O
</s>
<s>
In	O
March	O
2020	O
,	O
Elias	O
"	O
Jamppi	O
"	O
Olkkonen	O
filed	O
a	O
lawsuit	O
against	O
Valve	O
,	O
alleging	O
that	O
a	O
lifetime	O
VAC	B-Application
ban	I-Application
negatively	O
affected	O
his	O
esports	O
career	O
,	O
specifically	O
his	O
inability	O
to	O
play	O
in	O
Valve-sanctioned	O
Major	O
tournaments	O
,	O
which	O
subsequently	O
prevented	O
him	O
from	O
signing	O
onto	O
the	O
esports	O
team	O
OG	O
.	O
</s>
<s>
The	O
VAC-ban	O
is	O
tied	O
to	O
an	O
account	O
which	O
he	O
previously	O
owned	O
when	O
he	O
was	O
14	O
,	O
and	O
then	O
sold	O
to	O
a	O
friend	O
who	O
incurred	O
the	O
ban	O
;	O
the	O
lawsuit	O
alleges	O
that	O
a	O
lifelong	O
VAC	B-Application
ban	I-Application
for	O
a	O
minor	O
,	O
particularly	O
without	O
the	O
ability	O
to	O
first	O
plead	O
his	O
case	O
,	O
is	O
unreasonable	O
.	O
</s>
<s>
A	O
few	O
users	O
used	O
to	O
collect	O
VAC	B-Application
bans	I-Application
,	O
but	O
this	O
was	O
eventually	O
made	O
less	O
prolific	O
as	O
Valve	O
updated	O
the	O
VAC	B-Application
ban	I-Application
message	O
shown	O
on	O
the	O
user	O
's	O
profile	O
,	O
now	O
showing	O
"	O
Multiple	O
VAC	B-Application
bans	I-Application
on	O
record	O
"	O
instead	O
of	O
the	O
actual	O
number	O
of	O
VAC	B-Application
bans	I-Application
.	O
</s>
