利用网页上弹出来的小广告，把它拦截并替换为我们做好的内容，图片，网页，flash都可以，我这里举几个例子，我这里只是对特定的目标才做代理，其它网站是不走代理的，由于很多网站不止一个IP，所以这里用防火墙把目标添加到一个地址列表，用来做代理的目标地址，配合radius计费系统，把即将到期的用户下发另外一个IP段，再只对这个源地址做代理，实现提醒即将到期用户续费的目的,如果用户量多的话，想在哪个知名网站做点小广告，嘿嘿，再收取点广告赞助，

/ip firewall filter
add action=add-dst-to-address-list address-list=web_proxy \
    address-list-timeout=0s chain=forward comment="" content=www.baidu.com \
    disabled=no
add action=add-dst-to-address-list address-list=web_proxy \
    address-list-timeout=0s chain=forward comment="" content=img.5251.net \
    disabled=no
add action=add-dst-to-address-list address-list=web_proxy \
    address-list-timeout=0s chain=forward comment="" content=\
    bbs.routerclub.com disabled=no
add action=add-dst-to-address-list address-list=web_proxy \
    address-list-timeout=0s chain=forward comment="" content=\
    minisite2009.qq.com disabled=no

/ip firewall nat
add action=redirect chain=dstnat comment="" disabled=no dst-address-list=\
    web_proxy dst-port=80 protocol=tcp to-ports=923

/ip proxy
set always-from-cache=no cache-administrator=td0923@yahoo.cn cache-hit-dscp=4 \
    cache-on-disk=no enabled=yes max-cache-size=none max-client-connections=\
    600 max-fresh-time=3d max-server-connections=600 parent-proxy=0.0.0.0 \
    parent-proxy-port=0 port=923 serialize-connections=no src-address=0.0.0.0
/ip proxy access
add action=deny comment="" disabled=no path=/othercity/all.htm redirect-to=\
    192.168.30.2/qqpush.html
add action=deny comment="" disabled=no path=/img/baidu_logo.gif redirect-to=\
    192.168.30.2/logo.gif
add action=deny comment="" disabled=no path=/images/ad_router_club.gif \
    redirect-to=192.168.30.2/routerclub.gif
add action=deny comment="" disabled=no path=\
    /upload/2008-09-11/108841759409.gif redirect-to=192.168.30.2/00.gif