<s>
Simjacker	B-General_Concept
is	O
a	O
cellular	O
software	O
exploit	O
for	O
SIM	O
Cards	O
discovered	O
by	O
AdaptiveMobile	O
Security	O
.	O
</s>
<s>
The	O
attack	O
works	O
by	O
exploiting	O
a	O
vulnerability	O
in	O
a	O
UICC/SIM	O
Card	O
library	O
called	O
the	O
S	O
@T	O
Browser	O
.	O
</s>
<s>
A	O
specially	O
formatted	O
binary	O
text	O
message	O
is	O
sent	O
to	O
the	O
victim	O
handset	O
,	O
which	O
contains	O
a	O
set	O
of	O
commands	O
to	O
be	O
executed	O
by	O
the	O
S	O
@T	O
Browser	O
environment	O
in	O
the	O
UICC	B-Algorithm
.	O
</s>
<s>
As	O
the	O
S	O
@T	O
Browser	O
environment	O
has	O
access	O
to	O
a	O
subset	O
of	O
SIM	O
Toolkit	O
commands	O
,	O
the	O
attackers	O
used	O
this	O
vulnerability	O
to	O
instruct	O
the	O
UICC	B-Algorithm
to	O
request	O
IMEI	O
and	O
location	O
information	O
from	O
the	O
handset	O
via	O
SIM	O
Toolkit	O
commands	O
.	O
</s>
<s>
Once	O
this	O
was	O
obtained	O
the	O
UICC	B-Algorithm
then	O
instructs	O
the	O
handset	O
to	O
exfiltrate	O
this	O
information	O
to	O
the	O
attackers	O
within	O
another	O
text	O
message	O
.	O
</s>
<s>
The	O
Simjacker	B-General_Concept
attack	O
does	O
not	O
require	O
a	O
SIM	O
key	O
,	O
only	O
that	O
the	O
SIM	O
Card	O
has	O
the	O
S	O
@T	O
Browser	O
library	O
installed	O
on	O
it	O
,	O
and	O
that	O
the	O
binary	O
messages	O
containing	O
the	O
S	O
@T	O
Browser	O
commands	O
can	O
be	O
sent	O
to	O
the	O
victim	O
.	O
</s>
