HTTP GET请求发送到我的网站以获取未知的.php文件.为什么以及如何防止这种情况

我有一个部署在数字海洋液滴上的应用程序.部署后大约1天,我的服务器崩溃,最终日志如下所示:

GET /vehicle/tank/all/1 304 2.965 ms - -
GET /vehicle/tank/all/1 304 2.582 ms - -
GET /vehicle/tank/all/1 304 1.735 ms - -
GET /vehicle/tank/all/1 304 1.566 ms - -
GET http://dhg.pisz.pl/httptest.php 404 1.771 ms - 43
GET http://dhg.pisz.pl/httptest.php 404 3.271 ms - 43
GET http://dhg.pisz.pl/httptest.php 404 1.051 ms - 43
GET http://24x7-allrequestsallowed.com/?  PHPSESSID=aab45f4f00143PWZJTVBY%40DXJFV%5D 200 1.777 ms - 1878
GET / 200 2.794 ms - 1878
GET http://testp4.pospr.waw.pl/testproxy.php 404 2.617 ms - 52
HEAD /robots.txt 404 2.946 ms - 24
HEAD / 200 1.751 ms - 1878
GET http://dhg.pisz.pl/httptest.php 404 9.679 ms - 43

Error: Connection lost: The server closed the connection.
at Protocol.end (/root/tycho/node_modules/mysql/lib/protocol/Protocol.js:109:13)
at Socket. (/root/tycho/node_modules/mysql/lib/Connection.js:102:28)
at Socket.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16
at process._tickCallback (node.js:415:13)
[nodemon] app crashed - waiting for file changes before starting...

这是攻击吗？如果是这样,我该怎么做才能阻止客户端首先提出这些类型的获取请求？