HOME
|
IGCSE
N
ot
e
s
N
ot
e
s
M
i
s
cellane
ous
A
b
out
U
s
T
he
I
n
t
e
r
ne
t
&
i
t
'
s
us
e
s
T
op
ic
s
c
ov
e
r
ed
:
5
.
1
I
n
t
e
r
ne
t
and
t
he
W
or
ld
W
ide
W
eb
5
.
2
D
igi
t
al
C
urr
enc
y
5
.
3
C
y
be
r
S
ec
ur
i
ty
5
.
1
I
n
t
e
r
ne
t
and
t
he
W
or
ld
W
ide
W
eb
I
n
t
e
r
ne
t
U
s
e
s
tr
an
s
mi
ss
i
o
n
proto
c
o
l
s
su
ch
a
s
TCP
and
IP
(
I
n
t
e
r
ne
t
P
roto
c
o
l
s
)
A
ll
ows
t
he
us
e
r
to
c
o
mm
u
nica
t
e
w
i
t
h
ot
he
r
us
e
rs
v
ia
cha
t
,
email
,
calling
and
m
or
e
W
or
ld
w
ide
C
o
llec
t
i
o
n
o
f
I
n
t
e
r
c
o
nnec
t
ed
N
e
twor
k
s
and
D
e
v
ice
s
w
he
r
ea
s
W
or
ld
W
ide
W
eb
(
WWW
)
C
o
llec
t
i
o
n
o
f
w
eb
p
age
s
and
ot
he
r
inf
or
ma
t
i
o
n
o
n
w
eb
s
i
t
e
s
U
s
e
s
HTTP
(
S
)
proto
c
o
l
s
t
ha
t
a
r
e
wr
i
tt
en
us
ing
H
yp
e
rt
e
xt
M
a
r
k
-
up
L
ang
u
age
(
HTML
)
URL
s
(
U
nif
or
m
R
e
sour
ce
L
o
ca
tor
)
a
r
e
us
ed
f
or
t
he
l
o
ca
t
i
o
n
o
f
t
he
w
eb
p
age
s
W
eb
p
age
s
can
be
acce
ss
ed
b
y
w
eb
b
rows
e
rs
U
nif
or
m
R
e
sour
ce
L
o
ca
tor
(
URL
s
)
URL
s
a
r
e
us
ed
to
l
o
ca
t
e
and
acce
ss
w
eb
p
age
s
.
T
he
typ
ical
f
or
ma
t
o
f
URL
s
i
s
-
proto
c
o
l
://
w
eb
s
i
t
e
add
r
e
ss
/
p
a
t
h
/
fi
le
name
T
he
proto
c
o
l
(
s
e
t
o
f
ru
le
s
w
hile
s
ending
or
r
ecei
v
ing
da
t
a
o
n
t
he
in
t
e
r
ne
t
)
wou
ld
usu
all
y
be
HTTP
or
HTTPS
T
he
w
eb
s
i
t
e
add
r
e
ss
wou
ld
c
o
n
t
ain
-
d
o
main
h
ost
(
www
)
d
o
main
name
(
w
eb
s
i
t
e
name
)
d
o
main
typ
e
(.
c
o
m
, .
or
g
, .
ne
t
, .
g
ov
)
or
so
me
t
ime
s
c
ou
n
try
c
o
de
s
(.
u
k
, .
in
, .
c
y
)
T
he
p
a
t
h
wou
ld
usu
all
y
bec
o
me
t
he
fi
le
di
r
ec
tory
roots
.
f
or
e
x
am
p
le
,
h
ttps
://
www
.
z
n
ot
e
s
.
c
o
m
/
c
o
m
put
e
r
-
s
cience
T
he
/
c
o
m
put
e
r
-
s
cience
i
s
t
he
fi
le
name
HTTP
and
HTTPS
HTTP
st
and
s
f
or
H
yp
e
rt
e
xt
tr
an
s
fe
r
proto
c
o
l
and
HTTPS
st
and
s
f
or
H
yp
e
rt
e
xt
tr
an
s
fe
r
proto
c
o
l
s
ec
ur
e
T
he
y
a
r
e
s
afe
ty
proto
c
o
l
s
main
t
ained
w
hile
tr
an
s
mi
tt
ing
da
t
a
.
S
ec
ur
e
make
i
t
ha
r
de
r
f
or
u
na
ut
h
or
i
z
ed
us
e
rs
to
in
t
e
r
ce
pt
and
mani
pu
la
t
e
t
he
da
t
a
\
W
eb
B
rows
e
rs
I
t
i
s
so
f
tw
a
r
e
us
ed
to
acce
ss
w
eb
p
age
s
and
di
sp
la
y
o
n
t
he
in
t
e
r
ne
t
I
t
r
ende
rs
,
in
t
e
rpr
e
ts
and
tr
an
s
la
t
e
s
t
he
HTML
c
o
de
in
to
v
i
su
al
di
sp
la
y
f
or
t
he
us
e
r
en
sur
e
s
SSL
&
TLS
s
ec
ur
i
ty
can
be
e
st
abli
s
hed
O
ffe
rs
addi
t
i
o
nal
fea
tur
e
s
:
s
ea
r
ch
hi
story
ad
bl
o
cke
rs
S
tor
e
c
oo
kie
s
M
anage
m
u
l
t
i
p
le
t
ab
s
S
tor
e
b
oo
kma
r
k
s
P
rov
i
t
e
na
v
iga
t
i
o
n
too
l
s
\
R
e
tr
ie
v
al
and
L
o
ca
t
i
o
n
o
f
w
eb
p
age
s
:
→
d
o
ne
us
ing
t
he
DNS
(
d
o
main
name
and
s
e
rv
e
r
)
S
yst
em
C
o
m
put
e
r
typ
e
s
in
t
he
ur
l
B
rows
e
r
s
end
s
URL
to
t
he
d
o
main
name
s
e
rv
e
r
(
DNS
)
us
ing
a
proto
c
o
l
DNS
stor
e
s
inde
x
and
ma
t
che
s
w
i
t
h
t
he
IP
add
r
e
ss
in
i
t
’
s
stor
ed
da
t
aba
s
e
.
O
r
s
ea
r
che
s
in
an
ot
he
r
DNS
s
e
rv
e
r
u
n
t
il
i
t
ge
ts
t
he
add
r
e
ss
,
r
e
tr
ie
v
e
s
and
stor
e
s
i
t
in
t
he
da
t
aba
s
e
IP
i
s
r
e
tur
ned
to
t
he
w
eb
b
rows
e
r
B
rows
e
r
s
end
s
r
e
qu
e
st
to
t
he
w
eb
s
i
t
e
f
ro
m
a
w
eb
s
e
rv
e
r
B
rows
e
r
r
ende
rs
,
in
t
e
rpr
e
ts
t
he
HTML
and
di
sp
la
ys
v
i
su
al
da
t
a
C
oo
kie
s
C
oo
kie
s
a
r
e
s
mall
t
e
xt
fi
le
s
stor
ed
o
n
t
he
us
e
r
’
s
c
o
m
put
e
r
T
he
y
a
r
e
us
ed
to
tr
ack
da
t
a
ab
out
t
he
us
e
rs
and
a
utofi
ll
f
or
m
s
or
gi
v
e
su
gge
st
i
o
n
s
acc
or
dingl
y
T
yp
e
s
o
f
C
oo
kie
s
-
S
e
ss
i
o
n
C
oo
kie
s
P
e
rs
i
st
en
t
C
oo
kie
s
T
em
por
a
ry
c
oo
kie
s
w
hich
a
r
e
stor
ed
in
t
he
RAM
t
ill
t
he
b
rows
e
r
i
s
cl
os
ed
.
S
tor
ed
o
n
t
he
ha
r
d
di
s
k
o
n
t
he
c
o
m
put
e
r
u
n
t
il
t
hei
r
e
xp
i
ry
da
t
e
or
t
he
us
e
r
dele
t
e
s
t
hem
.
C
an
la
st
f
ro
m
w
eek
s
to
y
ea
rs
D
o
e
s
n
’
t
c
o
llec
t
an
y
p
e
rso
nal
inf
or
ma
t
i
o
n
o
n
t
he
us
e
r
’
s
la
ptop
U
s
ed
to
r
ec
or
d
us
e
r
’
s
pr
efe
r
ence
s
A
g
oo
d
e
x
am
p
le
i
s
t
he
v
i
rtu
al
s
h
opp
ing
ba
s
ke
t
o
n
e
-
c
o
mme
r
ce
w
eb
s
i
t
e
s
R
emembe
rs
t
he
us
e
r
’
s
l
o
gin
in
de
t
ail
s
so
t
he
us
e
r
d
o
e
s
n
’
t
ha
v
e
to
l
o
g
in
e
v
e
ry
t
ime
t
he
y
v
i
s
i
t
a
w
eb
s
i
t
e
5
.
2
D
igi
t
al
C
urr
enc
y
A
digi
t
al
c
urr
enc
y
i
s
a
typ
e
o
f
c
urr
enc
y
t
ha
t
e
x
i
sts
o
nl
y
in
elec
tro
nic
f
or
m
and
i
s
n
ot
backed
b
y
an
y
p
h
ys
ical
c
o
mm
o
di
ty
or
g
ov
e
r
nmen
t
.
O
nl
y
E
x
i
sts
E
lec
tro
nicall
y
D
igi
t
al
c
urr
encie
s
a
r
e
pur
el
y
elec
tro
nic
,
meaning
t
he
y
d
o
n
ot
e
x
i
st
in
p
h
ys
ical
f
or
m
like
tr
adi
t
i
o
nal
c
urr
encie
s
su
ch
a
s
ca
s
h
or
c
o
in
s
.
T
he
y
a
r
e
stor
ed
in
digi
t
al
w
alle
ts
or
acc
ou
n
ts
and
can
be
tr
an
s
fe
rr
ed
elec
tro
nicall
y
be
tw
een
indi
v
id
u
al
s
or
b
us
ine
ss
e
s
D
ecen
tr
ali
s
ed
M
an
y
digi
t
al
c
urr
encie
s
op
e
r
a
t
e
o
n
a
decen
tr
ali
s
ed
ne
twor
k
;
meaning
t
ha
t
t
he
y
a
r
e
n
ot
c
o
n
tro
lled
b
y
an
y
cen
tr
al
a
ut
h
or
i
ty
like
a
g
ov
e
r
nmen
t
or
fi
nancial
in
st
i
tut
i
o
n
I
n
st
ead
,
tr
an
s
ac
t
i
o
n
s
a
r
e
v
e
r
i
fi
ed
and
r
ec
or
ded
o
n
a
pu
blic
ledge
r
kn
ow
n
a
s
a
bl
o
ckchain
U
s
ed
f
or
T
r
an
s
ac
t
i
o
n
s
D
igi
t
al
c
urr
encie
s
can
be
us
ed
f
or
v
a
r
i
ous
tr
an
s
ac
t
i
o
n
s
,
incl
u
ding
pur
cha
s
ing
g
oo
d
s
and
s
e
rv
ice
s
o
nline
or
tr
an
s
fe
rr
ing
m
o
ne
y
in
t
e
r
na
t
i
o
nall
y
T
he
y
can
al
so
be
us
ed
f
or
in
v
e
st
men
ts
or
a
s
a
stor
e
o
f
v
al
u
e
V
o
la
t
ile
D
igi
t
al
c
urr
encie
s
can
be
highl
y
vo
la
t
ile
;
meaning
t
hei
r
v
al
u
e
can
flu
c
tu
a
t
e
r
a
p
idl
y
ov
e
r
s
h
ort
p
e
r
i
o
d
s
o
f
t
ime
T
hi
s
can
make
t
hem
r
i
s
k
y
in
v
e
st
men
ts
and
can
al
so
make
i
t
dif
fi
c
u
l
t
to
us
e
t
hem
a
s
a
st
able
stor
e
o
f
v
al
u
e
E
x
am
p
le
s
incl
u
de
B
i
t
c
o
in
,
E
t
he
r
e
u
m
,
L
i
t
ec
o
in
,
and
R
i
pp
le
F
or
m
o
f
p
a
y
men
t
to
p
a
y
f
or
g
oo
d
s
and
s
e
rv
ice
s
A
fe
w
e
x
am
p
le
s
a
r
e
D
ebi
t
/
C
r
edi
t
C
a
r
d
s
,
A
pps
(
P
a
yp
al
,
A
pp
le
P
a
y
,
B
ank
T
r
an
s
fe
rs
and
man
y
m
or
e
)
C
rypto
g
r
a
p
h
y
w
a
s
la
t
e
r
in
tro
d
u
ced
d
u
e
to
t
he
pro
blem
in
cen
tr
ali
z
ed
banking
syst
em
s
.
D
ecen
tr
ali
z
ed
-
n
ot
c
o
n
tro
lled
b
y
an
y
a
ut
h
or
i
ty
or
fi
nancial
in
st
i
tut
i
o
n
.
A
ll
fi
nance
s
a
r
e
r
ec
or
ded
in
a
pu
blic
ledge
r
called
bl
o
ckchain
.
C
rypto
c
urr
enc
y
us
e
s
c
rypto
g
r
a
p
h
y
to
main
t
ain
tr
ack
o
f
tr
an
s
ac
t
i
o
n
s
.
C
rypto
c
urr
enc
y
i
s
al
so
m
or
e
s
ec
ur
e
beca
us
e
i
t
us
e
s
B
l
o
ckchain
N
e
twor
k
B
l
o
ckchain
N
e
twor
k
B
l
o
ckchain
N
e
twor
k
in
vo
l
v
e
s
s
e
v
e
r
al
in
t
e
r
c
o
nnec
t
ed
c
o
m
put
e
rs
w
he
r
e
t
he
tr
an
s
ac
t
i
o
n
da
t
a
i
s
stor
ed
I
t
i
s
a
pu
blic
digi
t
al
ledge
r
t
ha
t
stor
e
s
e
v
e
ry
tr
an
s
ac
t
i
o
n
made
w
i
t
h
a
p
a
rt
ic
u
la
r
digi
t
al
c
urr
enc
y
H
acking
i
s
n
’
t
poss
ible
he
r
e
a
s
tr
an
s
ac
t
i
o
n
de
t
ail
s
wou
ld
be
s
en
t
to
all
t
he
c
o
m
put
e
rs
and
t
he
da
t
a
can
’
t
be
changed
w
i
t
h
out
t
he
c
o
n
s
en
t
o
f
all
t
he
ne
twor
k
membe
rs
B
l
o
ckchain
i
s
a
digi
t
al
ledge
r
t
ha
t
r
ec
or
d
s
e
v
e
ry
tr
an
s
ac
t
i
o
n
made
w
i
t
h
a
p
a
rt
ic
u
la
r
digi
t
al
c
urr
enc
y
E
ach
tr
an
s
ac
t
i
o
n
i
s
t
ime
-
st
am
p
ed
and
added
to
t
he
bl
o
ckchain
in
a
p
e
r
manen
t
and
u
nal
t
e
r
able
w
a
y
B
l
o
ckchain
i
s
a
decen
tr
ali
s
ed
t
echn
o
l
o
g
y
,
meaning
t
ha
t
i
t
i
s
n
ot
c
o
n
tro
lled
b
y
a
s
ingle
en
t
i
ty
or
a
ut
h
or
i
ty
I
n
st
ead
,
e
v
e
ry
p
a
rt
ici
p
an
t
in
t
he
ne
twor
k
ha
s
a
c
opy
o
f
t
he
ledge
r
and
can
v
e
r
if
y
t
he
tr
an
s
ac
t
i
o
n
s
inde
p
enden
t
l
y
T
he
bl
o
ckchain
i
s
made
up
o
f
"
bl
o
ck
s
"
o
f
tr
an
s
ac
t
i
o
n
s
t
ha
t
a
r
e
linked
to
ge
t
he
r
in
a
"
chain
"
us
ing
c
rypto
g
r
a
p
hic
alg
or
i
t
hm
s
T
hi
s
c
r
ea
t
e
s
a
s
ec
ur
e
and
t
am
p
e
r
-
proo
f
r
ec
or
d
o
f
e
v
e
ry
tr
an
s
ac
t
i
o
n
made
w
i
t
h
t
he
digi
t
al
c
urr
enc
y
E
ach
tr
an
s
ac
t
i
o
n
in
t
he
bl
o
ckchain
m
ust
be
v
e
r
i
fi
ed
b
y
m
u
l
t
i
p
le
p
a
rt
ici
p
an
ts
in
t
he
ne
twor
k
T
hi
s
v
e
r
i
fi
ca
t
i
o
n
pro
ce
ss
en
sur
e
s
t
ha
t
t
he
tr
an
s
ac
t
i
o
n
i
s
legi
t
ima
t
e
and
pr
e
v
en
ts
an
y
f
r
a
u
d
u
len
t
ac
t
i
v
i
ty
H
ow
d
o
bl
o
ckchain
s
wor
k
E
v
e
ry
t
ime
a
tr
an
s
ac
t
i
o
n
t
ake
s
p
lace
,
A
bl
o
ck
i
s
c
r
ea
t
ed
.
T
he
bl
o
ck
wou
ld
c
o
n
t
ain
D
a
t
a
-
N
ame
o
f
t
he
s
ende
r
and
t
he
r
ecei
v
e
r
,
am
ou
n
t
o
f
m
o
ne
y
and
m
or
e
H
a
s
h
V
al
u
e
-
U
ni
qu
e
v
al
u
e
gene
r
a
t
ed
b
y
an
alg
or
i
t
hm
P
r
e
v
i
ous
H
a
s
h
V
al
u
e
-
H
a
s
h
V
al
u
e
o
f
t
he
pr
e
v
i
ous
bl
o
ck
in
t
he
chain
T
he
first
bl
o
ck
i
s
called
t
he
gene
s
i
s
bl
o
ck
a
s
i
t
d
o
e
s
n
’
t
po
in
t
to
an
y
pr
e
v
i
ous
bl
o
ck
(
P
r
e
v
i
ous
H
a
s
h
V
al
u
e
-
0000
)
5
.
3
C
y
be
r
S
ec
ur
i
ty
c
y
be
r
s
ec
ur
i
ty
t
h
r
ea
ts
1
.
B
rut
e
F
or
ce
A
tt
ack
:
H
acke
rs
try
to
g
u
e
ss
your
p
a
sswor
d
b
y
try
ing
all
t
he
diffe
r
en
t
c
o
mbina
t
i
o
n
s
o
f
le
tt
e
rs
,
n
u
mbe
rs
and
sy
mb
o
l
s
.
E
ffec
t
:
H
acke
r
ge
ts
acce
ss
to
us
e
r
’
s
p
e
rso
nal
da
t
a
(
c
r
edi
t
ca
r
d
s
,
p
a
sswor
d
s
and
m
or
e
)
T
o
r
em
ov
e
r
i
s
k
:
U
s
e
stro
nge
r
p
a
sswor
d
s
w
i
t
h
m
or
e
cha
r
ac
t
e
rs
and
sy
mb
o
l
s
2
.
D
a
t
a
I
n
t
e
r
ce
pt
i
o
n
:
T
hi
s
in
vo
l
v
e
s
st
ealing
da
t
a
b
y
t
a
pp
ing
in
to
a
w
i
r
ed
or
a
w
i
r
ele
ss
tr
an
s
mi
ss
i
o
n
line
W
a
r
d
r
i
v
ing
-
T
he
ac
t
o
f
l
o
ca
t
ing
and
us
ing
w
i
r
ele
ss
in
t
e
r
ne
t
c
o
nnec
t
i
o
n
s
illegall
y
P
acke
t
S
nif
fi
ng
-
U
s
e
s
P
acke
t
s
niffe
rs
to
e
x
amine
p
acke
ts
s
en
t
ov
e
r
a
line
,
all
t
he
da
t
a
c
o
llec
t
ed
i
s
s
en
t
back
to
t
he
a
tt
acke
r
E
ffec
t
:
C
an
ca
us
e
a
c
o
m
put
e
r
to
c
r
a
s
h
C
an
dele
t
e
or
c
orrupt
fi
le
s
/
da
t
a
T
o
r
em
ov
e
r
i
s
k
:
I
n
st
all
an
t
i
-
v
i
rus
so
f
tw
a
r
e
D
o
n
’
t
us
e
so
f
tw
a
r
e
f
ro
m
u
nkn
ow
n
sour
ce
s
B
e
ca
r
ef
u
l
w
hen
op
ening
email
s
f
ro
m
u
nkn
ow
n
3
.
D
i
str
ib
ut
ed
D
enial
o
f
S
e
rv
ice
A
tt
ack
s
(
DD
o
S
)
A
n
a
tt
em
pt
a
t
pr
e
v
en
t
ing
us
e
rs
f
ro
m
acce
ss
ing
p
a
rt
o
f
a
ne
twor
k
W
hen
a
us
e
r
in
puts
a
w
eb
s
i
t
e
'
s
URL
in
to
t
hei
r
b
rows
e
r
,
a
r
e
qu
e
st
i
s
di
sp
a
t
ched
to
t
he
w
eb
s
e
rv
e
r
h
ous
ing
t
he
r
e
sp
ec
t
i
v
e
w
eb
s
i
t
e
or
w
eb
p
age
.
H
ow
e
v
e
r
,
t
he
s
e
rv
e
r
ha
s
limi
t
a
t
i
o
n
s
in
handling
a
sp
eci
fi
c
n
u
mbe
r
o
f
r
e
qu
e
sts
.
I
f
an
a
tt
acke
r
floo
d
s
i
t
w
i
t
h
t
h
ous
and
s
o
f
r
e
qu
e
sts
,
i
t
can
lead
to
ov
e
r
l
o
ad
,
r
ende
r
ing
t
he
s
e
rv
e
r
inca
p
able
o
f
s
e
rv
icing
legi
t
ima
t
e
us
e
r
r
e
qu
e
sts
.
T
hi
s
s
i
tu
a
t
i
o
n
c
o
n
st
i
tut
e
s
a
denial
o
f
s
e
rv
ice
.
I
n
t
he
ca
s
e
o
f
a
di
str
ib
ut
ed
denial
o
f
s
e
rv
ice
(
DD
o
S
)
a
tt
ack
,
t
he
malici
ous
tr
af
fi
c
or
igina
t
e
s
f
ro
m
n
u
me
rous
c
o
m
put
e
rs
,
making
i
t
challenging
to
effec
t
i
v
el
y
bl
o
ck
t
he
a
ss
a
u
l
t
.
U
su
all
y
t
em
por
a
ry
b
ut
ma
y
be
damaging
A
tt
acke
r
ma
y
be
able
to
pr
e
v
en
t
us
e
r
f
ro
m
:
A
cce
ss
ing
t
hei
r
email
s
A
cce
ss
ing
w
eb
s
i
t
e
s
A
cce
ss
ing
o
nline
s
e
rv
ice
s
4
.
H
acking
T
he
ac
t
o
f
gaining
illegal
acce
ss
to
a
c
o
m
put
e
r
syst
em
E
ffec
t
:
L
ead
s
to
iden
t
i
ty
t
hef
t
,
gaining
p
e
rso
nal
inf
or
ma
t
i
o
n
D
a
t
a
can
be
dele
t
ed
,
changed
or
c
orrupt
ed
T
o
r
em
ov
e
r
i
s
k
:
F
i
r
e
w
all
s
S
tro
ng
p
a
sswor
d
s
/
us
e
r
ID
s
U
s
e
o
f
an
t
i
-
hacking
so
f
tw
a
r
e
D
iffe
r
ence
be
tw
een
hacking
and
c
r
acking
H
acking
b
r
eak
s
in
to
c
o
m
put
e
r
syst
em
to
st
eal
da
t
a
C
r
acking
i
s
w
he
r
e
so
me
o
ne
edi
ts
a
pro
g
r
am
c
o
de
,
malici
ous
5
.
M
al
w
a
r
e
S
t
and
s
f
or
M
alici
ous
S
o
f
tw
a
r
e
,
A
fe
w
e
x
am
p
le
s
a
r
e
-
V
i
rus
-
P
ro
g
r
am
t
ha
t
can
r
e
p
lica
t
e
i
ts
elf
w
i
t
h
t
he
in
t
en
t
i
o
n
o
f
dele
t
ing
or
c
orrupt
ing
fi
le
s
,
ca
us
e
c
o
m
put
e
r
malf
u
nc
t
i
o
n
R
an
so
m
w
a
r
e
-
A
tt
acke
rs
enc
rypt
t
he
us
e
r
’
s
da
t
a
u
n
t
il
a
ce
rt
ain
am
ou
n
t
o
f
m
o
ne
y
i
s
p
aid
A
d
w
a
r
e
-
D
i
sp
la
ys
u
n
w
an
t
ed
ad
s
o
n
us
e
r
’
s
s
c
r
een
T
ro
jan
H
ors
e
-
P
ro
g
r
am
s
t
ha
t
a
r
e
di
s
g
u
i
s
ed
a
s
legi
t
ima
t
e
so
f
tw
a
r
e
S
pyw
a
r
e
-
S
end
s
da
t
a
ab
out
all
t
he
ac
t
i
v
i
t
ie
s
o
f
t
he
us
e
r
to
t
he
a
tt
acke
r
W
or
m
s
-
P
ro
g
r
am
s
t
ha
t
can
r
e
p
lica
t
e
i
ts
elf
w
i
t
h
t
he
in
t
en
t
i
o
n
o
f
c
orrupt
ing
t
he
en
t
i
r
e
ne
twor
k
in
st
ead
o
f
t
he
c
o
m
put
e
r
al
o
ne
6
.
P
hi
s
hing
A
tt
acke
rs
s
end
legi
t
ima
t
e
-
l
oo
king
email
s
to
bai
t
t
he
us
e
r
in
to
gi
v
ing
out
t
hei
r
inf
or
ma
t
i
o
n
.
T
o
r
em
ov
e
r
i
s
k
:
D
o
n
’
t
op
en
link
s
f
ro
m
u
nkn
ow
n
r
ecei
v
e
rs
U
s
e
an
t
i
-
p
hi
s
hing
too
l
s
B
l
o
ck
pop
-
up
ad
s
H
a
v
e
an
up
-
to
-
da
t
e
b
rows
e
r
7
.
P
ha
r
ming
T
he
a
tt
acke
r
in
st
al
s
a
malici
ous
c
o
de
o
n
t
he
c
o
m
put
e
r
w
hich
r
edi
r
ec
ts
t
he
us
e
r
to
fake
w
eb
s
i
t
e
s
E
ffec
t
:
U
s
e
r
gi
v
e
s
out
l
o
gin
de
t
ail
s
and
ot
he
r
p
e
rso
nal
de
t
ail
s
T
o
r
em
ov
e
r
i
s
k
:
U
s
ing
an
t
i
-
v
i
rus
so
f
tw
a
r
e
C
hecking
t
he
sp
elling
and
t
he
w
eblink
ca
r
ef
u
ll
y
M
aking
sur
e
t
ha
t
t
he
g
r
een
p
adl
o
ck
i
s
pr
e
s
en
t
in
t
he
URL
ba
r
8
.
S
o
cial
E
nginee
r
ing
A
tt
acke
rs
c
r
ea
t
e
a
so
cial
s
i
tu
a
t
i
o
n
w
hich
lead
s
to
v
ic
t
im
s
gi
v
ing
out
t
hei
r
de
t
ail
s
(
F
or
e
x
am
p
le
-
S
p
am
call
s
inf
or
ming
t
ha
t
your
acc
ou
n
t
ha
s
been
hacked
)
K
ee
p
ing
da
t
a
s
afe
f
ro
m
t
h
r
ea
ts
.
A
cce
ss
L
e
v
el
s
-
H
a
v
ing
D
iffe
r
en
t
le
v
el
s
o
f
acce
ss
f
or
diffe
r
en
t
p
e
op
le
(
f
or
e
x
am
p
le
-
O
nl
y
d
o
c
tors
can
ha
v
e
acce
ss
to
p
a
t
ien
t
’
s
da
t
a
)
.
A
n
t
i
v
i
rus
-
P
rot
ec
ts
us
e
r
’
s
c
o
m
put
e
r
f
ro
m
mal
w
a
r
e
a
tt
ack
s
.
A
ut
hen
t
ica
t
i
o
n
-
U
s
e
r
prov
ing
w
h
o
t
he
y
a
r
e
.
M
ost
c
o
mm
o
n
me
t
h
o
d
s
a
r
e
p
a
sswor
d
s
,
PIN
s
,
M
o
bile
s
(
OTP
s
),
bi
o
me
tr
ic
s
and
m
or
e
)
.
B
i
o
me
tr
ic
s
-
typ
e
o
f
a
ut
hen
t
ica
t
i
o
n
t
ha
t
us
e
s
a
u
ni
qu
e
h
u
man
cha
r
ac
t
e
r
i
st
ic
,
su
ch
a
s
fi
nge
rpr
in
ts
,
vo
ice
or
r
e
t
ina
bl
oo
d
v
e
ss
el
p
a
tt
e
r
n
B
ene
fits
and
D
r
a
w
back
s
o
f
V
a
r
i
ous
B
i
o
me
tr
ic
M
e
t
h
o
d
B
i
o
me
tr
ic
M
e
t
h
o
d
s
B
ene
fits
D
r
a
w
back
s
F
inge
rpr
in
t
S
can
s
M
ost
de
v
el
op
men
t
M
e
t
h
o
d
,
V
e
ry
ea
sy
to
us
e
,
R
e
qu
i
r
e
s
v
e
ry
l
ow
stor
age
to
stor
e
t
he
bi
o
me
tr
ic
da
t
a
I
n
trus
i
v
e
a
s
us
ed
to
iden
t
if
y
c
r
iminal
s
,
C
an
’
t
be
us
ed
if
t
he
fi
nge
r
ge
ts
di
rty
or
damaged
(
e
.
g
.
c
uts
)
R
e
t
ina
S
can
V
e
ry
high
acc
ur
ac
y
,
I
m
poss
ible
to
r
e
p
lica
t
e
a
p
e
rso
n
’
s
r
e
t
ina
V
e
ry
in
trus
i
v
e
,
T
ake
s
l
o
nge
r
to
v
e
r
if
y
,
E
xp
en
s
i
v
e
to
in
st
all
and
s
e
t
up
F
ace
R
ec
o
gni
t
i
o
n
N
o
n
-
in
trus
i
v
e
me
t
h
o
d
,
R
ela
t
i
v
el
y
chea
p
e
r
C
an
’
t
iden
t
if
y
if
t
he
r
e
a
r
e
an
y
change
s
in
t
he
ligh
t
ing
,
change
in
age
or
p
e
rso
n
’
s
age
.
V
o
ice
R
ec
o
gni
t
i
o
n
N
o
n
-
I
n
trus
i
v
e
me
t
h
o
d
,
v
e
r
i
fi
ca
t
i
o
n
i
s
d
o
ne
qu
ickl
y
and
r
ela
t
i
v
el
y
chea
p
e
r
V
o
ice
s
can
be
r
ec
or
ded
and
us
ed
f
or
v
e
r
i
fi
ca
t
i
o
n
,
l
ow
acc
ur
ac
y
,
illne
ss
e
s
su
ch
a
s
c
o
ld
or
c
ou
gh
can
affec
t
a
p
e
rso
n
’
s
vo
ice
making
iden
t
i
fi
ca
t
i
o
n
im
poss
ible
.
.
T
wo
-
S
t
e
p
V
e
r
i
fi
ca
t
i
o
n
-
R
e
qu
i
r
e
s
two
me
t
h
o
d
s
o
f
a
ut
hen
t
ica
t
i
o
n
to
prov
e
w
h
o
t
he
us
e
r
i
s
.
A
uto
ma
t
ic
S
o
f
tw
a
r
e
U
p
da
t
e
s
-
L
a
t
e
st
up
da
t
e
s
c
o
n
t
ain
p
a
t
che
s
w
hich
im
prov
e
de
v
ice
s
ec
ur
i
ty
.
S
p
elling
and
T
o
ne
-
F
ake
email
s
t
end
to
ha
v
e
wro
ng
sp
elling
and
g
r
amma
r
(
ama
zo
nn
in
st
ead
o
f
ama
zo
n
),
and
t
he
to
ne
wou
ld
al
so
s
eem
ur
gen
t
.
F
i
r
e
w
all
s
-
H
a
r
d
w
a
r
e
or
S
o
f
tw
a
r
e
w
hich
m
o
ni
tors
t
he
tr
af
fi
c
be
tw
een
a
ne
twor
k
and
t
he
us
e
r
’
s
c
o
m
put
e
r
A
fir
e
w
all
can
be
so
f
tw
a
r
e
or
ha
r
d
w
a
r
e
ba
s
ed
I
t
m
o
ni
tors
inc
o
ming
and
out
g
o
ing
tr
af
fi
c
be
tw
een
t
he
c
o
m
put
e
r
and
t
he
ne
twor
k
and
kee
ps
a
l
o
g
o
f
t
he
tr
af
fi
c
T
he
us
e
r
s
e
ts
c
r
i
t
e
r
ia
f
or
t
he
tr
af
fi
c
(
t
hi
s
i
s
called
t
he
w
hi
t
eli
st
/
blackli
st
)
and
t
he
tr
af
fi
c
i
s
c
o
m
p
a
r
ed
w
i
t
h
t
hi
s
T
he
fir
e
w
all
w
ill
acce
pt
or
r
ejec
t
t
he
tr
af
fi
c
ba
s
ed
o
n
t
hi
s
and
an
ale
rt
can
be
s
en
t
to
t
he
us
e
r
I
t
can
hel
p
pr
e
v
en
t
hacking
and
malici
ous
so
f
tw
a
r
e
t
ha
t
c
ou
ld
be
a
t
h
r
ea
t
to
t
he
s
ec
ur
i
ty
o
f
t
he
da
t
a
.
P
roxy
S
e
rv
e
rs
-
A
c
ts
a
s
an
in
t
e
r
media
t
e
be
tw
een
t
he
us
e
r
’
s
c
o
m
put
e
r
and
t
he
w
eb
s
e
rv
e
r
.
T
he
y
a
r
e
us
ed
f
or
-
F
il
t
e
r
ing
I
n
t
e
r
ne
t
tr
af
fi
c
b
y
us
ing
a
s
e
t
o
f
c
r
i
t
e
r
ia
.
O
nl
y
if
c
r
i
t
e
r
ia
ma
t
che
s
d
o
e
s
t
he
s
i
t
e
acce
ss
be
all
ow
ed
.
E
l
s
e
i
t
i
s
denied
and
t
he
us
e
r
i
s
n
ot
i
fi
ed
.
K
ee
p
ing
t
he
us
e
r
’
s
IP
A
dd
r
e
ss
C
o
n
fi
den
t
ial
B
l
o
cking
acce
ss
to
ce
rt
ain
w
eb
s
i
t
e
s
A
tt
ack
s
like
DD
o
S
and
H
acking
a
tt
ack
t
he
proxy
s
e
rv
e
r
kee
p
ing
t
he
w
eb
s
e
rv
e
r
s
afe
A
c
ts
a
s
a
fir
e
w
all
a
s
w
ell
. \
.
P
r
i
v
ac
y
S
e
tt
ing
s
-
U
s
ed
to
limi
t
o
n
w
h
o
can
acce
ss
and
s
ee
us
e
r
’
s
profi
le
P
r
i
v
ac
y
s
e
tt
ing
s
a
r
e
us
ed
to
c
o
n
tro
l
t
he
am
ou
n
t
o
f
p
e
rso
nal
inf
or
ma
t
i
o
n
t
ha
t
i
s
s
ha
r
ed
o
nline
T
he
y
a
r
e
an
im
port
an
t
mea
sur
e
to
pr
e
v
en
t
iden
t
i
ty
t
hef
t
and
ot
he
r
f
or
m
s
o
f
o
nline
f
r
a
u
d
U
s
e
rs
s
h
ou
ld
r
eg
u
la
r
l
y
r
e
v
ie
w
t
hei
r
pr
i
v
ac
y
s
e
tt
ing
s
and
adj
ust
t
hem
a
s
needed
.
SSL
(
S
ec
ur
e
S
o
cke
t
L
a
y
e
r
)
-
S
e
t
o
f
ru
le
s
us
ed
w
hile
c
o
mm
u
nica
t
ing
w
i
t
h
ot
he
r
us
e
rs
o
n
t
he
in
t
e
r
ne
t
.
SSL
i
s
a
s
ec
ur
i
ty
proto
c
o
l
w
hich
i
s
us
ed
to
enc
rypt
da
t
a
tr
an
s
mi
tt
ed
ov
e
r
t
he
in
t
e
r
ne
t
T
hi
s
hel
ps
to
pr
e
v
en
t
ea
v
e
s
d
ropp
ing
and
ot
he
r
f
or
m
s
o
f
in
t
e
r
ce
pt
i
o
n
SSL
i
s
w
idel
y
us
ed
to
prot
ec
t
o
nline
tr
an
s
ac
t
i
o
n
s
,
su
ch
a
s
t
h
os
e
in
vo
l
v
ing
c
r
edi
t
ca
r
d
inf
or
ma
t
i
o
n
or
ot
he
r
s
en
s
i
t
i
v
e
da
t
a
I
t
wor
k
s
b
y
s
ending
a
digi
t
al
ce
rt
i
fi
ca
t
e
to
t
he
us
e
r
’
s
b
rows
e
r
T
hi
s
c
o
n
t
ain
s
t
he
pu
blic
ke
y
w
hich
can
be
us
ed
f
or
a
ut
hen
t
ica
t
i
o
n
O
nce
t
he
ce
rt
i
fi
ca
t
e
i
s
a
ut
hen
t
ica
t
ed
,
t
he
tr
an
s
ac
t
i
o
n
w
ill
begin
M
en
u
|
P
r
e
v
i
ous
U
ni
t
|
N
e
xt
U
ni
t
I
f
you
ha
v
e
an
y
qu
e
r
ie
s
,
c
o
m
p
lain
ts
or
su
gge
st
i
o
n
s
,
feel
f
r
ee
to
wr
i
t
e
us
o
n
our
email
:
stu
d
ysy
nc
.
ig
@
gmail
.
c
o
m
