<s>
A	O
cancelbot	B-Protocol
is	O
an	O
automated	O
or	O
semi-automated	O
process	O
for	O
sending	O
out	O
third-party	O
cancel	O
messages	O
over	O
Usenet	B-Application
,	O
commonly	O
as	O
a	O
stopgap	O
measure	O
to	O
combat	O
spam	O
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
uses	O
of	O
a	O
cancelbot	B-Protocol
was	O
by	O
microbiology	O
professor	O
Richard	O
DePew	O
,	O
to	O
remove	O
anonymous	O
postings	O
in	O
science	O
newsgroups	O
.	O
</s>
<s>
Perhaps	O
the	O
most	O
well	O
known	O
early	O
cancelbot	B-Protocol
was	O
used	O
in	O
June	O
1994	O
by	O
Arnt	O
Gulbrandsen	O
within	O
minutes	O
of	O
the	O
first	O
post	O
of	O
Canter	O
&	O
Siegel	O
's	O
second	O
spam	O
wave	O
,	O
as	O
it	O
was	O
created	O
in	O
response	O
to	O
their	O
"	O
Green	O
Card	O
spam	O
"	O
in	O
April	O
1994	O
.	O
</s>
<s>
Usenet	B-Application
spammers	O
have	O
alleged	O
that	O
cancelbots	B-Protocol
are	O
a	O
tool	O
of	O
the	O
mythical	O
Usenet	B-Application
cabal	O
.	O
</s>
<s>
Cancelbots	B-Protocol
must	O
follow	O
community	O
consensus	O
to	O
be	O
able	O
to	O
serve	O
a	O
useful	O
purpose	O
,	O
and	O
historically	O
,	O
technical	O
criteria	O
have	O
been	O
the	O
only	O
acceptable	O
criteria	O
for	O
determining	O
if	O
messages	O
are	O
cancelable	O
,	O
and	O
only	O
a	O
few	O
active	O
cancellers	O
ever	O
obtain	O
the	O
broad	O
community	O
support	O
needed	O
to	O
be	O
effective	O
.	O
</s>
<s>
Pseudosites	O
are	O
referenced	O
in	O
cancel	O
headers	O
by	O
legitimate	O
cancelbots	B-Protocol
to	O
identify	O
the	O
criteria	O
on	O
which	O
a	O
message	O
is	O
being	O
canceled	O
,	O
allowing	O
administrators	O
of	O
Usenet	B-Application
sites	O
to	O
determine	O
via	O
standard	O
"	O
aliasing	O
"	O
mechanisms	O
which	O
criteria	O
that	O
they	O
will	O
accept	O
third-party	O
cancels	O
for	O
.	O
</s>
<s>
Pseudosite	O
Criterion	O
Breidbart	O
Index	O
above	O
the	O
cancel	O
threshold	O
for	O
the	O
group	O
or	O
hierarchy	O
cyberspam	O
!	O
usenet	B-Application
"	O
Make	O
money	O
fast	O
"	O
schemes	O
mmfcancel	O
!	O
cyberspam	O
!	O
usenet	B-Application
"	O
Spew	O
"	O
(	O
large	O
number	O
of	O
nonsense	O
or	O
repeated	O
postings	O
)	O
spewcancel	O
!	O
cyberspam	O
!	O
usenet	B-Application
Binary	O
files	O
posted	O
to	O
a	O
group	O
that	O
does	O
n't	O
allow	O
them	O
bincancel	O
!	O
cyberspam	O
!	O
usenet	B-Application
Retromoderation	O
(	O
only	O
applies	O
to	O
groups	O
that	O
have	O
a	O
retromoderation	O
policy	O
in	O
place	O
)	O
retromod	O
!	O
cyberspam	O
!	O
usenet	B-Application
Ad	O
cancels	O
within	O
the	O
biz	O
.	O
</s>
<s>
The	O
$alz	B-Application
convention	O
states	O
that	O
the	O
Message-Id	O
:	O
header	O
used	O
for	O
a	O
third-party	O
cancel	O
should	O
always	O
be	O
the	O
original	O
Message-Id	O
:	O
with	O
"	O
cancel.	O
"	O
</s>
<s>
The	O
X-Canceled-By	O
:	O
convention	O
states	O
that	O
the	O
operator	O
of	O
a	O
cancelbot	B-Protocol
should	O
provide	O
a	O
consistent	O
,	O
valid	O
,	O
and	O
actively	O
monitored	O
contact	O
email	O
address	O
for	O
their	O
cancelbot	B-Protocol
in	O
the	O
X-Canceled-By	O
:	O
header	O
,	O
both	O
to	O
identify	O
the	O
canceler	O
,	O
and	O
to	O
provide	O
a	O
point	O
of	O
contact	O
in	O
case	O
something	O
goes	O
wrong	O
or	O
questions	O
arise	O
regarding	O
the	O
cancelbot	B-Protocol
's	O
operations	O
.	O
</s>
