How can i block "strafe" ?

[omer]

I'm running hlds 7561 version. Some users using strafe hack on my zombie(biohazard) server. Pls give me some trick.
Alias codes

alias "lvo" "-forward; cl_yawspeed -1300; +left; +moveleft; wait; cl_yawspeed 400; -left; -moveleft"
alias "dno" "-forward; cl_yawspeed -1300; +right; +moveright; wait; cl_yawspeed 400; -right; -moveright"
alias "+ss" "alias _special @ss; @ss"
alias "-ss" "alias _special"
alias "@ss" "special; lvo; dno"
alias "fps" "developer 1; fps_max 250; fps_modem 250"
bind KEY "+ss; fps"
toggleconsole
echo "Strafe Script by 1LX"

 

[Mistrick]

#include <amxmodx>
#include <fakemeta>

public plugin_init()
{
    register_plugin("Left/Right block", "0.1", "dev-cs.ru");
    register_forward(FM_PlayerPreThink, "FM_PlayerPreThink_Pre", false);
}
public FM_PlayerPreThink_Pre(id)
{
    if(!is_user_alive(id)) return FMRES_IGNORED;

    new bButtons = pev(id, pev_button);

    if(bButtons & (IN_LEFT | IN_RIGHT))
    {
        new Float:fVelocity[3]; pev(id, pev_velocity, fVelocity);
        fVelocity[0] *= 0.2; fVelocity[1] *= 0.2;
        set_pev(id, pev_velocity, fVelocity);
    }

    return FMRES_IGNORED;
}

 

[omer]

thx <3