I've got a snippet here, saying it all about mirai virus

/*
	=================================================================================
	Name : wdt_test.c
	Version : 0.1
	Copyright (C) 2012 by Andre Wussow, 2012, desk@binerry.de
	Description :
	A simple test for working with the Raspberry Pi BCM2835 Watchdog.
	References :
	http://binerry.de/post/28263824530/raspberry-pi-watchdog-timer
	================================================================================
	This sample is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License as published by the Free Software Foundation; either
	version 2.1 of the License, or (at your option) any later version.
	This sample is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	Lesser General Public License for more details.
	================================================================================
	*/
	#include <stdio.h>
	#include <fcntl.h>
	#include <linux/watchdog.h>
	int main (int argc, char *argv[])
	{
	// print infos
	printf("Raspberry Pi BCM2835 Watchdog Sample\n");
	printf("========================================\n");
	int deviceHandle;
	int disableWatchdog = 1;
	// test watchdog reset via t-param
	if (argc > 1) {
	if (!strncasecmp(argv[1], "-t", 2)) {
	disableWatchdog = 0;
	}
	}
	printf("Disabling watchdog before closing device: %d\n", disableWatchdog);
	// open watchdog device on /dev/watchdog
	if ((deviceHandle = open("/dev/watchdog", O_RDWR | O_NOCTTY)) < 0) {
	printf("Error: Couldn't open watchdog device! %d\n", deviceHandle);
	return 1;
	}
	// get timeout info of watchdog (try to set it to 15s before)
	int timeout = 15;
	ioctl(deviceHandle, WDIOC_SETTIMEOUT, &timeout);
	ioctl(deviceHandle, WDIOC_GETTIMEOUT, &timeout);
	printf("The watchdog timeout is %d seconds.\n\n", timeout);
	// feed watchdog 3 times with heartbeats
	int i;
	for (i = 0; i < 3; i++) {
	printf("Feeding the dog with a heartbeat.\n");
	ioctl(deviceHandle, WDIOC_KEEPALIVE, 0);
	sleep(10);
	}
	if (disableWatchdog)
	{
	printf("Disable watchdog.\n");
	write(deviceHandle, "V", 1);
	}
	// close connection and return
	close(deviceHandle);
	return 0;
	} https://github.com/binerry/RaspberryPi/blob/master/snippets/c/watchdog/wdt_test.c