近年來，如何去防範網路攻擊是一直是被研究的領域，攻擊者會在進行攻擊時隱藏自己，讓防禦者或是調查人員無法掌握背後的攻擊者。其中，物聯網 (Internet of Things) 設備將越來越多，其所產生的安全問題也隨之一一浮上檯面。像是針對物聯網設備進行攻擊的惡意程式 Mirai，抑或是針對預設密碼的網路攝影機的攻擊等等，都已慢慢侵害到一般人的隱私或是進而造成危害。其中造成世界危害的攻擊包含影響網路狀況的 DDoS 攻擊、垃圾郵件散布、漏洞挖掘、使用者隱私洩露等等，這些攻擊將會因物聯網設備的增加而更難防禦。然而，對於物聯網設備的偵測與防禦還正處在萌芽階段，在本篇論文當中，將從垃圾郵件的角度來提出一個 IoTD 的方法，用於偵測寄送信件的寄信人是否為一台物聯網設備，進而有效利用此資訊在未來的安全研究領域之中，讓物聯網的安全性問題能更進一步的有所斬獲。

In recent years, how to prevent cyber attacks has always been in the field of research. Attackers will hide when they are attacking so that defenders or investigators cannot grasp the attackers behind them. Among them, the security problems of the increment of the Internet of Things (IoT) will come to the forefront. Mirai, a malware attacking IoT devices, and the problem on a network camera with default password issue, harm and leak the privacy of innocent people. The attacks cause harm to the world such as DDoS attacks that affect network bandwidth, email spam, vulnerability mining, user privacy leaks, and etc. These attacks will be more difficult to defend due to the increase in IoT devices. However, the detection and defense of IoT devices are still in its infancy. In this paper, an IoTD method will be proposed from the perspective of spam to detect whether a sender of the mail is an IoT device, and thus effectively use this information in security research field in the future.

摘要v
Abstract vi
致謝vii
Contents viii
List of Figures x
List of Tables xi
1 Introduction 1
2 Background 4
2.1 E-mail Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 SMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Transport Layer Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Threat Model 11
4 System design 13
4.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2 System overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 Evaluation 18
5.1 System environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2 Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6 Related Work 22
7 Discussion 23
8 Conclusion 24
Reference 25
A Analysis 27

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