<s>
Trojan:Win32/FakeSysdef	O
,	O
originally	O
dispersed	O
as	O
an	O
application	O
called	O
"	O
HDD	O
Defragmenter	O
"	O
hence	O
the	O
name	O
"	O
FakeSysdef	B-Protocol
"	O
or	O
"	O
Fake	O
System	O
Defragmenter	O
"	O
,	O
is	O
a	O
Trojan	O
targeting	O
the	O
Microsoft	B-Application
Windows	I-Application
operating	I-Application
system	I-Application
that	O
was	O
first	O
documented	O
in	O
late	O
2010	O
.	O
</s>
<s>
Win32/FakeSysdef	O
manifests	O
as	O
one	O
or	O
more	O
of	O
an	O
array	O
of	O
programs	O
that	O
purport	O
to	O
scan	O
one	O
's	O
computer	O
for	O
hardware	O
failures	O
related	O
to	O
system	O
memory	O
,	O
hard	O
drives	O
and	O
system	O
functionality	O
as	O
a	O
whole	O
.	O
</s>
<s>
Everyday	O
numerous	O
fake	O
antivirus	B-Application
and	O
security	O
applications	O
are	O
published	O
and	O
released	O
to	O
unsuspecting	O
end-users	O
via	O
a	O
large	O
assortment	O
of	O
distribution	O
channels	O
.	O
</s>
<s>
The	O
programs	O
often	O
have	O
an	O
icon	O
in	O
the	O
notification	O
area	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
desktop	O
and	O
constantly	O
display	O
pop-up	O
messages	O
alerting	O
the	O
user	O
about	O
fake	O
security	O
issues	O
such	O
as	O
virus	O
infections	O
.	O
</s>
<s>
The	O
Win32/FakeSysdef	O
installer	O
may	O
arrive	O
in	O
the	O
computer	O
with	O
various	O
file	O
names	O
.	O
</s>
<s>
When	O
run	O
,	O
the	O
installer	O
drops	O
and	O
injects	O
a	O
DLL	O
file	O
(	O
or	O
sometimes	O
and	O
EXE	O
file	O
)	O
into	O
common	O
processes	O
,	O
for	O
example	O
"	O
EXPLORER.EXE	B-Protocol
"	O
,	O
"	O
WINLOGON.EXE	O
"	O
,	O
and	O
"	O
WININET.EXE	O
"	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
the	O
EXE	O
is	O
set	O
to	O
run	O
at	O
every	O
Windows	O
restart	O
and	O
the	O
DLL	O
is	O
injected	O
into	O
"	O
EXPLORER.EXE	B-Protocol
"	O
by	O
the	O
"	O
EXE	O
"	O
component	O
.	O
</s>
<s>
Additionally	O
,	O
some	O
Win32/FakeSysdef	O
variants	O
that	O
may	O
terminate	O
running	O
processes	O
during	O
installation	O
and	O
may	O
block	O
launched	O
application	O
after	O
the	O
computer	O
restarts	O
.	O
</s>
<s>
After	O
the	O
restart	O
,	O
FakeSysdef	B-Protocol
attempts	O
to	O
block	O
every	O
launched	O
program	O
,	O
and	O
may	O
then	O
display	O
fake	O
error	O
messages	O
offering	O
to	O
fix	O
the	O
problem	O
.	O
</s>
<s>
Win32/FakeSysdef	O
displays	O
numerous	O
false	O
alerts	O
indicating	O
system	O
errors	O
while	O
displaying	O
the	O
appearance	O
of	O
scanning	O
the	O
hard	O
disk	O
and	O
defragmenting	O
it	O
,	O
then	O
prompts	O
the	O
user	O
,	O
with	O
a	O
"	O
Fix	O
Errors	O
"	O
button	O
,	O
to	O
buy	O
and	O
activate	O
it	O
to	O
fix	O
discovered	O
errors	O
.	O
</s>
<s>
When	O
the	O
"	O
Fix	O
Errors	O
"	O
button	O
is	O
selected	O
,	O
FakeSysdef	B-Protocol
pretends	O
to	O
scan	O
and	O
defragment	O
the	O
hard	O
disk	O
.	O
</s>
<s>
Anti-virus	B-Application
software	I-Application
makers	O
responded	O
to	O
the	O
threat	O
of	O
FakeSysdef	B-Protocol
by	O
adding	O
checks	O
for	O
it	O
in	O
their	O
products	O
.	O
</s>
<s>
Simple	O
removal	O
of	O
the	O
software	O
enabled	O
by	O
this	O
is	O
sometimes	O
not	O
enough	O
to	O
reverse	O
the	O
damage	O
to	O
configuration	O
files	O
that	O
FakeSysdef	B-Protocol
was	O
known	O
to	O
edit	O
.	O
</s>
